Plant antimicrobial compositions including an emulsifier and/or ozone and methods of use

ABSTRACT

Compositions and methods that utilize a combination of essential oils or other plant-derived extracts or compounds and an emulsifier as an antimicrobial are provided. In some embodiments the compositions further include ozone. In some embodiments, the composition includes one or more plant essential oils, plant extracts, or plant-derived compounds, or combinations thereof, and an emulsifier (such as a saponin). The antimicrobial composition may also include water, peracetic acid, acetic acid, lactic acid, citric acid, and/or hydrogen peroxide. Methods of killing a microorganism, including contacting the microorganism with the disclosed antimicrobial compositions are also provided. The microorganism may be present on a food item or a food contact of non-food contact surface and may be in the form of a biofilm. In some examples, the antimicrobial composition is used one or more times (such as 1 to 5 times).

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/704,950, filed Dec. 5, 2019, which claims the benefit of U.S.Provisional Application No. 62/775,724, filed Dec. 5, 2018, each ofwhich are incorporated by reference herein in its entirety.

ACKNOWLEDGMENT OF GOVERNMENT SUPPORT

This invention was made with government support under grant numberUSDA-NIFA-OREI 2010-51300-21760 awarded by the United States Departmentof Agriculture-National Institute of Food and Agriculture-OrganicAgriculture Research and Extension Initiative and grant number USDA-NIFA2016-68007-25064 awarded by the United States Department ofAgriculture-National Institute of Food and Agriculture. The governmenthas certain rights in the invention.

FIELD

This disclosure relates to antimicrobial compositions and methods,particularly utilizing essential oils, plant extracts, or otherplant-derived compounds in combination with emulsifiers and/or ozone.

BACKGROUND

The contamination of fresh produce by foodborne pathogens results in 9.5million illnesses in the United States each year causing $39 billion inmedical losses (Scharff, J. Food Prot. 75:123-131, 2012). Transfer ofpathogens to produce can happen in the field or during post-harvestwashing (Kumar et al., Curr. Opin. Food. Sci. 19:138-144, 2018;Macarisin et al., Foodborne Pathog. and Dis. 92(2):160-167, 2012; PerezRodriguez et al., Food Microbiol. 28:694-701, 2011; Ravishankar andKumar, Arizona Iceberg Lettuce Research Council Report 2014).Effectively reducing or eliminating pathogenic microorganisms from washwater during packing and processing is challenging as wash water cancontain plant exudates, debris, and organic matter that can reduce theefficacy of oxidative sanitizers such as chlorine (Dev Kumar andMicallef, Foodborne Pathog. Dis. 14(5):293-301, 2017; Gil et al., Int.J. Food. Microbiol. 134:37-45, 2009). For example, iceberg lettuce canbe contaminated by pathogens such as Salmonella enterica which mayattach to open stomata, fissures in the cuticle or trichome (Benjamin etal., Int. J. Food. Microbiol. 165:65-76, 2013; Golberg et al., Int. J.Food. Microbiol. 145:250-257, 2011; Takeuchi and Frank, J. Food. Prot.64:147-151, 2001). Post-harvest washing is an important step to reducecontamination by foodborne pathogens on lettuce leaves, since theseproducts are usually consumed raw.

Chlorine is a sanitizer commonly used by the produce industry (Kumar etal., Microbial Control and Food Preservation, Springer, pages 199-223,2017). The efficacy of chlorine decreases with reuse and the byproductsof chlorine can have adverse health effects. Safer and more efficaciousalternatives to chlorine are essential because of recurring foodborneoutbreaks associated with food products, such as leafy greens.

SUMMARY

Essential oils from herbs and spices have been shown to exhibitantimicrobial properties. Numerous essential oils have shownantimicrobial activity in vitro against different foodborne pathogenssuch as Escherichia coli, Campylobacter jejuni, Salmonella enterica, andListeria monocytogenes. Essential oils fall under the GenerallyRecognized as Safe (GRAS) status and can be used as sanitizers for thewashing of produce without the risk of adverse health effects to theconsumer and the environment. Olive extract and other plant-derivedcompounds, such as oregano oil, have demonstrated antimicrobial activityagainst Salmonella on leafy greens.

Ozone (O₃) is an allotrope of oxygen used for the disinfection ofbottled water and waste water treatment. Ozone is approved by the UnitedStates Food and Drug Administration for use as a disinfectant orsanitizer in the gas or liquid phase on food including meat and poultryand has GRAS status. Ozone is effective against a broad range ofGram-positive and Gram-negative bacteria.

Disclosed herein are compositions and methods that utilize a combinationof essential oils or other plant-derived extracts or compounds and anemulsifier as an antimicrobial. In some embodiments the compositions andmethods further include ozone. In some embodiments, the compositionincludes one or more plant essential oils, plant extracts, and/orplant-derived compounds and an emulsifier (such as a saponin). In otherexamples, the compositions include two or more (such as 2, 3, 4, ormore) plant essential oils, plant extracts, and/or plant-derivedcompounds and an emulsifier. The antimicrobial composition may alsoinclude water, peracetic acid, acetic acid, lactic acid, citric acid,and/or hydrogen peroxide. In some examples, the remainder of thecomposition is water.

In some examples, the composition includes one or more plant essentialoils, such as oregano oil, lemongrass oil, cinnamon oil, allspice oil,clovebud oil, mint oil, or a combination of two or more thereof. Inother examples, the composition includes one or more plant-derivedcompounds, such as carvacrol, eugenol, citral, cinnamaldehyde, thymol,or a combination of two or more thereof. The plant essential oil orplant-derived compound may be present in the composition at aconcentration of about 0.01-1% (v/v). In other examples, the compositionincludes a plant extract, such as olive extract, apple extract,grapeseed extract, potato peel extract, melon peel extract, apple peelextract, orange peel extract, hibiscus aqueous extract, green tea, blacktea, or decaffeinated black tea extract, mushroom extract, or rice hullsmoke extract. The plant extract may be present in the composition at aconcentration of about 1-10% (v/v). In some embodiments, the emulsifieris present in the composition at a concentration of about 0.0001-1%(v/v). In some examples, the emulsifier is a saponin (such as Quillajasaponin). In embodiments including ozone, the ozone is present in thecomposition at a concentration of about 0.1-10 mg/L.

In some embodiments are methods of killing a microorganism, includingcontacting the microorganism (for example, an item or surfacecontaminated with the microorganism) with a disclosed antimicrobialcomposition. In some examples, the microorganism (or an item or surfacecontaminated with the microorganism) is contacted with the disclosedantimicrobial composition in a solution, as a powder, in a vapor phase,a fog state, or an edible film. The microorganism may be a bacterium(such as Salmonella enterica, Escherichia coli, Listeria monocytogenes,Staphylococcus aureus, Clostridium perfringens, Vibrio parahaemolyticus,Campylobacter, Shigella, or Shiga toxin producing E. coli), viable butnon-culturable bacteria, bacterial spores, helminth, protozoan, fungus,or virus. The microorganism may be present on a food item (such as aproduce item or meat item) or a food contact or non-food contact surface(such as a truck, ship, crate, food processing plant, equipment,packaging material, wall, drain, conveyer belt, or floor). In someexamples, the microorganism is present on the food item or food contactor non-food contact surface in the form of a biofilm.

In some examples, the antimicrobial composition is used one or moretimes (such as 1 to 5 times). In embodiments including ozone, ozone maybe added to the composition one or more times, or in some examples isadded to the composition substantially continuously.

The foregoing and other features of the disclosure will become moreapparent from the following detailed description, which proceeds withreference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing S. Newport population (log CFU/g) on iceberglettuce leaves after washing for 60, 90 and 120 min in ozone, ozone+0.1%oregano oil, ozone+1% olive extract, and ozone+5% olive extract.

FIG. 2 is a graph showing comparative evaluation of the antimicrobialefficacy of ozone+saponin (0.0001%), ozone+saponin (0.0001%)+oliveextract (1%) and ozone+oregano oil (0.1%)+saponin (0.0001%)+oliveextract (1%) against S. Newport for 20 minutes (survivors shown in logCFU/g) on iceberg lettuce leaves.

FIG. 3 is a graph showing the effectiveness of individual andcombination essential oil treatments at 0.05% concentration. Oregano oil(00), lemongrass oil (LG), cinnamon oil (CO) and dual and triple (3×)combination treatments were tested.

FIG. 4 is a graph showing the effectiveness of individual andcombination treatments with LG, CO, OO, and dual and triple combinationsat 0.025% concentration.

FIG. 5 is a graph showing the efficacy of essential oil combinationsgiving a final concentration of 0.025%.

DETAILED DESCRIPTION I. Terms

Unless otherwise noted, technical terms are used according toconventional usage. Definitions of common terms in molecular biology maybe found in Lewin's Genes X, ed. Krebs et al., Jones and BartlettPublishers, 2009 (ISBN 0763766321); Kendrew et al. (eds.), TheEncyclopedia of Molecular Biology, published by Blackwell Publishers,1994 (ISBN 0632021829); Robert A. Meyers (ed.), Molecular Biology andBiotechnology: a Comprehensive Desk Reference, published by Wiley, John& Sons, Inc., 1995 (ISBN 0471186341); and George P. Rédei, EncyclopedicDictionary of Genetics, Genomics, Proteomics and Informatics, 3^(rd)Edition, Springer, 2008 (ISBN: 1402067534), and other similarreferences.

Unless otherwise explained, all technical and scientific terms usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which this disclosure belongs. The singular terms“a,” “an,” and “the” include plural referents unless the context clearlyindicates otherwise. Similarly, the word “or” is intended to include“and” unless the context clearly indicates otherwise. Hence “comprisingA or B” means including A, or B, or A and B.

Although methods and materials similar or equivalent to those describedherein can be used in the practice or testing of the present disclosure,suitable methods and materials are described below. All publications,patent applications, patents, and other references mentioned herein areincorporated by reference in their entirety. In case of conflict, thepresent specification, including explanations of terms, will control. Inaddition, the materials, methods, and examples are illustrative only andnot intended to be limiting.

In order to facilitate review of the various embodiments of thedisclosure, the following explanations of specific terms are provided:

Bacteria: Any of various prokaryotic organisms, including organismswithin various phyla in the Kingdom Procaryotae. The terms encompass allmicroorganisms commonly regarded as bacteria, including Mycoplasma,Chlamydia, Actinomyces, Streptomyces, and Rickettsia. The term alsoincludes cocci, bacilli, spirochetes, spheroplasts, protoplasts, and soforth. The term bacteria includes Gram-negative and Gram-positivebacteria, as well as viable, but non-culturable bacteria.

Biofilm: An aggregate of microorganisms in which cells that are embeddedwithin a self-produced matrix of extracellular polymeric substances(EPSs) adhere to each other and/or to a surface. The EPS matrix, whichis also referred to as slime, is a polymeric conglomeration generallycomposed of extracellular biopolymers (e.g., polysaccharides andproteins) in various structural forms.

Decontamination: To substantially inactivate or remove unwantedmicroorganisms or bacterial or fungal spores, for example by killing asubstantial number of microorganisms present. In some examples,decontamination with the disclosed antimicrobial compositions kills atleast 25%, at least 50%, at least 75%, at least 80%, at least 90%, atleast 95%, at least 99%, at least 99.9%, at least 99.99%, or at least99.999% of microorganisms present following contact with thecomposition. For example, decontamination with the disclosedantimicrobial compositions reduces the number of microorganisms (such asbacteria) present by at least 1-log, at least 2-logs, at least 3-logs,at least 4-logs, at least 5-logs, or more (for example as compared to notreatment).

Emulsifier: A compound or combination of compounds that increases ormaintains suspension or dispersion of one liquid in another, for examplea mixture of an oil and water. Exemplary emulsifiers include saponins,algin, carrageenan, agar, gum arabic, and lecithins. In some examples,emulsifiers also have surfactant and/or detergent-like properties.

Microorganism: Any of various bacteria, viruses, fungi, and protozoathat can cause disease or death to humans, animals, or plants, or otherbiological organisms.

Pathogenic spores are spores that are produced from a pathogen.Particular examples of pathogens that can produce spores include, butare not limited to, members of the genera Bacillus, Clostridium,Desulfotomaculans, Sporolactobacillus, Sporosarcina, and pathogenicfungi. In some examples the spore is referred to as an oocyst, such asthose produced by members of the Phylum Apicomplexa (such as Plasmodiumfalciparum and Cryptosporidium parvum).

II. Antimicrobial Compositions

Provided herein are antimicrobial compositions. In some embodiments, thedisclosed compositions include one or more essential oils, plantextracts, and/or plant-derived compounds and one or more emulsifiers. Insome examples, the compositions include two or more plant essentialoils, plant extracts, and/or plant-derived compounds (such as 2, 3, 4,or more; e.g., two or more essential oils) and one or more emulsifiers.In other embodiments, the disclosed compositions include one or moreessential oils, plant extracts, and/or plant-derived compounds, one ormore emulsifiers, and ozone. In other examples, the compositions includetwo or more plant essential oils, plant extracts, and/or plant-derivedcompounds (such as 2, 3, 4, or more; e.g., two or more essential oils),one or more emulsifiers, and ozone. In further embodiments, thecompositions include one or more essential oils or plant-derivedcompounds and ozone. Exemplary antimicrobial compositions include thoseprovided in Table 1. In some examples, the remainder of the compositionis water or another liquid. In other examples, the composition furtherincludes one or more additional sanitizers, for example, one or more ofperacetic acid, acetic acid, lactic acid, citric acid, or hydrogenperoxide.

In some embodiments, the compositions include one or more essential oils(such as 2, 3, 4, or more essential oils) in combination with one ormore emulsifiers and optionally ozone. Essential oils include, but arenot limited to, oregano oil, cinnamon oil, lemongrass oil, clove (e.g.,clovebud) oil, citrus oil, thyme oil, rosemary oil, bay leaf oil, staranise oil, mint oil, patchouli oil, vetiver oil, cardamom oil, sage oil,or allspice oil. In some examples, the essential oil is present in thecomposition at a concentration of about 0.01-1% (v/v), for example,about 0.01-0.025% (v/v), about 0.25%-0.05% (v/v), about 0.05-0.1% (v/v),about 0.1-0.3% (v/v), about 0.2-0.5% (v/v), about 0.4-0.7% (v/v), about0.6-0.8% (v/v), or about 0.7-1% (v/v). In other examples, the essentialoil is present in the composition at a concentration of at least about0.01% (v/v), at least about 0.025% (v/v), at least about 0.05% (v/v), atleast about 0.1% (v/v), about least about 0.125% (v/v), at least about0.2% (v/v), at least about 0.25% (v/v), at least about 0.3% (v/v), atleast about 0.4% (v/v), at least about 0.5% (v/v), at least about 0.6%(v/v), at least about 0.7% (v/v), at least about 0.8% (v/v), at leastabout 0.9% (v/v), or at least about 1% (v/v).

In some specific, non-limiting examples, the composition includes 0.01%(v/v), 0.025% (v/v), 0.05% (v/v), 0.1%, (v/v) 0.3% (v/v), 0.5% (v/v),0.7%, or 1% oregano oil, cinnamon oil, lemongrass oil, or combinationsof two or more thereof. In some embodiments, the composition includes acombination of essential oils (such as 2, 3, 4, or more essential oils)and the final concentration of essential oils in the composition is atleast about 0.01% (v/v), at least about 0.025% (v/v), at least about0.05% (v/v), at least about 0.1% (v/v), about least about 0.125% (v/v),at least about 0.2% (v/v), at least about 0.25% (v/v), at least about0.3% (v/v), at least about 0.4% (v/v), at least about 0.5% (v/v), atleast about 0.6% (v/v), at least about 0.7% (v/v), at least about 0.8%(v/v), at least about 0.9% (v/v), or at least about 1% (v/v).

In other embodiments, the compositions include one or more (such as 2,3, 4, or more) plant-derived compounds in combination with one or moreemulsifiers and/or ozone. Exemplary plant-derived compounds includecarvacrol, citral, cinnamaldehyde, eugenol, salicylaldehyde, geraniol,isoeugenol, terpineol, perillaldehyde, estragole, thymol, and menthol,or combinations of two or more thereof. In some examples, theplant-derived compound is present in the composition at a concentrationof about 0.01-1% (v/v), for example, about 0.01-0.025% (v/v), about0.25%-0.05% (v/v), about 0.05-0.1% (v/v), about 0.1-0.3% (v/v), about0.2-0.5% (v/v), about 0.4-0.7% (v/v), about 0.6-0.8% (v/v), or about0.7-1% (v/v). In other examples, the plant-derived compound is presentin the composition at a concentration of at least about 0.01% (v/v), atleast about 0.025% (v/v), at least about 0.05% (v/v), at least about0.1% (v/v), about least about 0.125% (v/v), at least about 0.2% (v/v),at least about 0.25% (v/v), at least about 0.3% (v/v), at least about0.4% (v/v), at least about 0.5% (v/v), at least about 0.6% (v/v), atleast about 0.7% (v/v), at least about 0.8% (v/v), at least about 0.9%(v/v), or at least about 1% (v/v). In some specific, non-limitingexamples, the composition includes 0.1%, (v/v) 0.3% (v/v), 0.5%, 0.7%,or 1% (v/v) carvacrol, 0.5%, 0.7%, or 1% citral, or 0.5%, 0.7%, or 1%cinnamaldehyde.

In further embodiments, the compositions include one or more (such as 2,3, 4, or more) plant extracts in combination with one or moreemulsifiers and/or ozone. Exemplary plant extracts include oliveextract, apple extract, grapeseed extract, potato peel extract, melonpeel extract, orange peel extract, apple peel extract, hibiscus aqueousextract, green tea, black tea, and decaffeinated black tea extracts,mushroom extract, and rice hull smoke extract. Methods of preparingplant extracts are known to one of ordinary skill in the art (see, e.g.,Medicinal Aromatic Plants 4:196, 2015). In some examples, the plantextract is present in the composition at a concentration of about 1-10%(v/v), for example, about 1-2.5% (v/v), about 2-4% (v/v), about 3-5%(v/v), about 6-8% (v/v), or about 7-10% (v/v). In other examples, theplant extract is present in the composition at a concentration of atleast about 1% (v/v), at least about 1.5% (v/v), at least about 2%(v/v), at least about 2.5% (v/v), at least about 3% (v/v), at leastabout 4% (v/v), at least about 5% (v/v), at least about 6% (v/v), atleast about 7% (v/v), at least about 8% (v/v), at least about 9% (v/v),or at least about 10% (v/v). In some specific, non-limiting examples,the composition includes 1%, 5%, or 7% (v/v) olive extract, 5% or 7%apple extract, or 5% or 7% grapeseed extract.

In additional embodiments, the compositions include one or moreessential oils, one or more plant-derived compounds, one or more plantextracts, or combinations of two or more thereof and one or moreemulsifiers and/or ozone. In some examples, the composition includes oneor more essential oils and one or more plant extracts with one or moreemulsifiers and/or ozone. One non-limiting example is a compositionincluding oregano oil and olive extract, saponin, and ozone.

In various embodiments, the composition includes an emulsifier. Theaddition of an emulsifier can promote formation of a stable emulsion,particularly of essential oils, in water, thereby increasing thesolubility of the oil in the composition. The emulsifier may also havesurfactant and/or detergent properties. Exemplary emulsifiers includesaponins, gum arabic, mustard, lecithin (such as soy or egg lecithin),carrageenan, guar gum, mono- and diglycerides, polysorbates, and sodiumdodecyl sulfate. In some non-limiting examples, the emulsifier is asaponin. Saponins are plant-derived amphipathic glycosides that havefoaming properties when shaken in an aqueous solution. Saponins can beobtained from plants including trees (such as maple (family Aceraceae),horse chestnut (family Hippocastanaceae)), ginseng, Gynostemmapentaphyllum, and Quillaja saponaria, beans and legumes (such as peasand soybeans), yucca (e.g., Yucca schidigera), and plants such assoaproot or soapberry. In some examples, the emulsifier is present inthe composition at a concentration of about 0.0001-1% (v/v), forexample, about 0.0001-0.0005% (v/v), about 0.0003-0.0007% (v/v), about0.0004-0.001% (v/v), about 0.001-0.005% (v/v), about 0.002-0.01% (v/v),about 0.01-0.1% (v/v), about 0.05-0.5% (v/v), about 0.25-0.75% (v/v), orabout 0.5-1% (v/v). In other examples, the emulsifier is present in thecomposition at a concentration of at least about 0.0001% (v/v), aboutleast about 0.0002% (v/v), at least about 0.0005% (v/v), at least about0.0007% (v/v), at least about 0.001% (v/v), at least about 0.003% (v/v),at least about 0.005% (v/v), at least about 0.007% (v/v), at least about0.01% (v/v), at least about 0.025% (v/v), at least about 0.05% (v/v), atleast about 0.1% (v/v), at least about 0.25% (v/v), at least about 0.5%(v/v), at least about 0.75% (v/v), or at least about 1% (v/v). In somespecific, non-limiting examples, the composition includes 0.0001% (v/v),0.002% (v/v), 0.005% (v/v), or 0.01% (v/v) Quillaja saponin.

In various embodiments, the composition also includes ozone. Ozone canbe generated using an ozone generator (for example, ForeverOzone™,OG-5G-BB). Ozone can be introduced in a solution such as thecompositions disclosed herein using a sparger. In some examples, thecomposition is around 1-4° C., to increase retention of ozone in theaqueous phase. In some examples, ozone is present in the composition ata concentration of about 0.1-10 mg/L, for example about 0.1-0.25 mg/L,about 0.2-0.5 mg/L, about 0.4-0.8 mg/L, about 0.7-1 mg/L, 1-5 mg/L, 2-6mg/L, 4-8 mg/L, or about 7-10 mg/L. In other examples, ozone is presentin the composition at a concentration of at least about 0.1 mg/L, atleast about 0.15 mg/L, at least about 0.2 mg/L, at least about 0.25mg/L, at least about 0.3 mg/L, at least about 0.4 mg/L, at least about0.5 mg/L at least about 0.6 mg/L, at least about 0.7 mg/L, at leastabout 0.8 mg/L, at least about 0.9 mg/L, at least about 1 mg/L, at leastabout 2 mg/L, at least about 3 mg/L, at least about 4 mg/L, at leastabout 5 mg/L, at least about 6 mg/L, at least about 7 mg/L, at leastabout 8 mg/L, at least about 9 mg/L, at least about 10 mg/L. In somespecific, non-limiting examples, the composition includes about 0.2 mg/Lozone. In other non-limiting examples, the composition includes about1-5 mg/L ozone. In other examples, ozone is present in the compositionat about 3-8 ppm or about 0.75 ppm (for example, in a dump tank). Insome examples, ozone is added to the composition periodically orcontinuously (for example to compensate for loss of aqueous ozone due toquenching by organic matter, off gassing and relatively short half-lifeof the ozone molecule).

Non-limiting examples of specific antimicrobial compositions includethose shown in Table 1.

TABLE 1 Exemplary antimicrobial compositions Essential Oil/Plantcompound Quillaja saponin Ozone 0.3% (v/v) oregano oil 0.005% (v/v) 0.1%(v/v) oregano oil 0.01% (v/v) lemongrass oil 0.01% (v/v) 0.025% (v/v)lemongrass oil 0.01% (v/v) 0.05% (v/v) lemongrass oil 0.01% (v/v) 0.125%(v/v) lemongrass oil 0.005% (v/v) 0.5% (v/v) lemongrass oil 0.0001%(v/v) 0.01% (v/v) oregano oil 0.01% (v/v) 0.025% (v/v) oregano oil 0.01%(v/v) 0.05% (v/v) oregano oil 0.01% (v/v) 0.1% (v/v) oregano oil 0.0001%(v/v) 1-10 mg/L 0.3% (v/v) oregano oil 0.0001% (v/v) 1-10 mg/L 0.5%(v/v) oregano oil 0.0001% (v/v) 0.7% (v/v) oregano oil 0.0001% (v/v)0.01% (v/v) cinnamon oil 0.01% (v/v) 0.025% (v/v) cinnamon oil 0.01%(v/v) 0.05% (v/v) cinnamon oil 0.01% (v/v) 0.125% (v/v) cinnamon oil0.005% (v/v) 0.5% (v/v) cinnamon oil 0.0001% (v/v) 0.1% (v/v) carvacrol0.0001% (v/v) 1-10 mg/L 0.3% (v/v) carvacrol 0.0001% (v/v) 1-10 mg/L0.5% (v/v) carvacrol 0.0001% (v/v) 1-10 mg/L 0.7% (v/v) carvacrol0.0001% (v/v) 1% (v/v) carvacrol 0.0001% (v/v) 0.5% (v/v) citral 0.0001%(v/v) 0.7% (v/v) citral 0.0001% (v/v) 1% (v/v) citral 0.0001% (v/v) 0.5%(v/v) cinnamaldehyde 0.0001% (v/v) 0.7% (v/v) cinnamaldehyde 0.0001%(v/v) 1% (v/v) cinnamaldehyde 0.0001% (v/v) 1% (v/v) olive extract0.0001% (v/v) 1-10 mg/L 5% (v/v) olive extract 0.0001% (v/v) 1-10 mg/L5% (v/v) olive extract 0.0001% (v/v) 7% (v/v) olive extract 0.0001%(v/v) 5% (v/v) apple extract 0.0001% (v/v) 7% (v/v) apple extract0.0001% (v/v) 5% (v/v) grapeseed extract 0.0001% (v/v) 7% (v/v)grapeseed extract 0.0001% (v/v) 0.05% (v/v) lemongrass oil + 0.01% (v/v)0.05% (v/v) cinnamon oil 0.05% (v/v) lemongrass oil + 0.01% (v/v) 0.05%(v/v) oregano oil 0.05% (v/v) oregano oil + 0.01% (v/v) 0.05% (v/v)cinnamon oil 0.05% (v/v) lemongrass oil + 0.01% (v/v) 0.05% (v/v)cinnamon oil + 0.05% (v/v) oregano oil 0.025% (v/v) lemongrass oil +0.01% (v/v) 0.025% (v/v) cinnamon oil 0.025% (v/v) lemongrass oil +0.01% (v/v) 0.025% (v/v) oregano oil 0.025% (v/v) oregano oil + 0.01%(v/v) 0.025% (v/v) cinnamon oil 0.025% (v/v) lemongrass oil + 0.01%(v/v) 0.025% (v/v) cinnamon oil + 0.025% (v/v) oregano oil 0.025% (v/v)lemongrass oil + 0.01% (v/v) cinnamon oil (evenly divided) 0.025% (v/v)lemongrass oil + 0.01% (v/v) cinnamon oil (evenly divided) 0.025% (v/v)lemongrass oil + 0.01% (v/v) oregano oil (evenly divided) 0.025% (v/v)oregano oil + 0.01% (v/v) cinnamon oil (evenly divided) 0.025% (v/v)lemongrass oil + 0.01% (v/v) cinnamon oil + oregano oil (evenly divided)

In additional embodiments, the compositions disclosed herein alsoinclude one or more additional sanitizing components, such as peraceticacid, acetic acid, lactic acid, or citric acid, or hydrogen peroxide.For example, in some examples, the composition includes about 1-100 ppmperacetic acid, acetic acid, lactic acid, or citric acid, such as about1-10 ppm, about 5-15 ppm, about 10-20 ppm, about 20-40 ppm, about 25-50ppm, about 50-75 ppm, or about 75-100 ppm peracetic acid, acetic acid,lactic acid, or citric acid. In other examples, the composition includesabout 1 ppm, about 5 ppm, about 10 ppm, about 15 ppm, about 20 ppm,about 25 ppm, about 30 ppm, about 40 ppm, about 50 ppm, about 75 ppm, orabout 100 ppm peracetic acid, acetic acid, lactic acid, or citric acid.In other examples, the composition includes about 1-6% hydrogenperoxide, such as about 1-3%, about 2-4%, about 3-5%, or about 4-6%hydrogen peroxide. In other examples, the composition includes about 1%,about 1.5%, about 2%, about 2.5%, about 3%, about 3.5%, about 4%, about4.5%, about 5%, about 5.5%, or about 6% hydrogen peroxide.

In some examples, the disclosed compositions are included in a solution(such as a wash solution or irrigation water) for decontamination ormicrobial control on food or other items. However, the compositions canalso be included in additional formulations, such as edible food itemsor edible films. In one example, the composition is included in a saladdressing. In other examples, the composition is included in ready-to-eatfood items such as coleslaw, egg salad, chicken salad, potato salad,pasta salad, ready-to-eat meats, and party dips and dipping sauces suchas salsas, and guacamole. Dairy products such as raw milk and rawcheeses, seafood products, ground meats, hamburger patties, meat cuts,meat chops, dehydrated food items, soups, pasta, pizza, and canned foodsmay also include the disclosed compositions.

III. Methods of Use

Methods of using the disclosed compositions as a decontaminant, forexample to kill undesired microorganisms or pathogens, are providedherein. The methods include contacting one or more microorganisms with adisclosed antimicrobial composition. The methods can be used todecontaminate an article (such as laboratory equipment, a produce item,or raw meat) or a surface (such as those in a building, house, office,food processing plant, cargo holds on transportation vessels such asairplanes, trucks, trains and ships, crates, counters, cutting boards,equipment, packaging material, wall, drain, conveyer belt, and non-foodcontact surfaces such as floors and floor drains) that is actually orpotentially contaminated with one or more undesired microorganisms. Insome examples, the article to be decontaminated is a produce or meat orfish item. In such examples, to decontaminate the article, for exampleby killing microorganisms present on the surface of the article, thearticle can be contacted with the composition in the form of a solution,for example by applying the composition to the surface of the article(e.g., by pouring, spraying, or misting the composition onto thesurface, by wiping the surface with a solid substrate including thecomposition, such as a towel or wipe), by immersing the article in acontainer containing the composition, or rinsing the article with thecomposition. In other examples, the article is contacted with a vaporphase containing the composition (for example, in a bag or containerduring packing). See, e.g., Reyes-Jurado et al. (Crit. Rev. Food Sci.doi.org/10.1080/10408398.2019.1586641, 2019), incorporated herein byreference in its entirety). In further examples, the microbialcomposition may be used as a powder, in the form of an edible film or asa coating on packaging (such as paper packaging). See e.g., Peretto etal. (Postharvest Biol. Technol. 89:11-18, 2014); Rodriguez et al. (Prog.Organic Coatings 60:33-38, 2007), both of which are incorporated byreference in their entirety.

In particular examples, the antimicrobial composition is used one ormore times to decontaminate an article or surface (or batches ofarticles or surfaces). For example, the antimicrobial composition can beused 1, 2, 3, 4, 5, or more times. In some examples, additional ozonemay be added to the composition between uses or substantiallycontinuously during use, to compensate for quenching of ozone duringuse. In some examples, the additional ozone may also improve the colorof the wash water.

In other examples, the disclosed methods include sequentially contactingthe article with two or more compositions. In one example, an article iscontacted with ozonated water, and then a disclosed composition issubsequently added to the ozonated water and the article is contactedwith the wash including the composition and ozone. In an alternativeexample, an article is contacted with a disclosed composition, and thenozone is added to the composition and the article is contacted with thewash including the antimicrobial, emulsifier, and ozone. In furtherexamples, an article is contacted with a disclosed composition, and thearticle is subsequently contacted with an ozonated wash.

In one example, the item to be decontaminated is a produce item, such asthe surface of a fruit or vegetable, such as tomatoes, leafy greens(such as spring mix, iceberg lettuce, romaine lettuce, baby spinach,mature spinach, kale, arugula, or radicchio), herbs, radishes, onions,scallions, sprouts (such as alfalfa sprouts or mung bean sprouts),cucumbers, apples, grapes, peaches, nectarines, plums, berries, melons(such as cantaloupe or honeydew), celery, leeks, green onions, cilantro,cabbage, cauliflower, broccoli, carrots, and the like. In otherexamples, the item to be decontaminated is a meat item, such as a pieceof raw meat from a cow, pig, or chicken, such as chicken breasts,thighs, wings, or legs, steaks, ground beef, ribs, roasts, and the like.In some examples, the item to be decontaminated is a seafood item, suchas a fish or shellfish. In other examples, the item to be decontaminatedis a dairy item (such as milk or cheese) or a ready-to-eat food item.Thus, the disclosed compositions can be used to kill adulterants in foodproducts, such as undesired microorganisms.

In other examples, the item to be decontaminated is a food contactand/or non-food contact surface (such as counters, containers,transports, floors, drains, floors, walls, equipment, conveyer belts,packaging, and the like). Exemplary surface materials include but arenot limited to stainless steel, plastic (for example, HDPE, PVC, or PC),glass, copper alloys, and rubber (for example, nitrile (BUNA-N) rubber).

In some examples, the method can further include rinsing the article orsurface after it has been contacted with the antimicrobial composition,for example the surface can be rinsed with water. In a specific example,the article is a produce, meat, or fish product that is rinsed withwater after it has been contacted with the antimicrobial composition.

Thus, provided herein are methods of killing a microorganism (e.g.,bacterium, bacterial spore, fungal spore, protozoan, or virus), bycontacting the microorganism with an antimicrobial composition providedherein. In one example, the bacterium killed is Escherichia coli (e.g.,E. coli O157:H7). In another example, the bacterium killed is Salmonellaenterica (such as Salmonella enterica serovar Newport). In otherexamples, the bacterium killed is Listeria monocytogenes. In someembodiments, the microorganism is present on a food item or surface(such as a food contact and/or non-food contact surface) in the form ofa biofilm.

In some examples, the microorganism is killed within 10 minutes, within15 minutes, within 20 minutes, within 30 minutes, within 60 minutes,within 90 minutes, or within 120 minutes (such as within 10-30 minutes,20-60 minutes 45-90 minutes, or 90-120 minutes) of contacting it withthe antimicrobial composition. In some examples, not all of themicroorganisms contacted with the composition are killed, but thecomposition is still an antimicrobial composition. For example, in someexamples at least 25%, at least 50%, at least 75%, at least 80%, atleast 90%, at least 95%, at least 99%, at least 99.9%, at least 99.99%,or at least 99.999% of the microorganisms (such as an at least 10-fold,at least 20-fold, at least 30-fold, at least 40-fold, at least 50-fold,or at least 100-fold reduction) are killed within 10 minutes, within 20minutes, within 30 minutes, within 60 minutes, within 90 minutes, orwithin 120 minutes (such as within 10-30 minutes, 20-60 minutes 45-90minutes, or 90-120 minutes) of contacting it with the antimicrobialcomposition.

In some examples, the method reduces a number of viable microorganismsby at least 1-log₁₀ compared to in the absence of treatment or a controltreatment. Thus, in some examples, the method reduces a number of viablemicroorganisms by at least 1-log₁₀ (such as at least 1-login, at least2-login, at least 3-login, at least 4-login, at least 5-log₁₀, at least6-login, at least 7-login, at least 8-login, or at least 9-log₁₀).

Methods for assaying for pathogen growth or viability are known in theart. Although particular examples are provided herein, the disclosure isnot limited to such methods.

Exemplary microorganisms that can be killed using the antimicrobialcompositions and methods disclosed herein include bacteria, viruses,protozoa, nematodes, and fungi. In particular embodiments, thecompositions and methods can kill bacteria. Exemplary Gram-negativebacteria that can be killed using the antimicrobial compositionsprovided herein include, but are not limited to: Escherichia coli (e.g.,K-12, O157:H7, other shiga-toxin producing strains [STEL]), Salmonellaenterica (including Salmonella enterica serovar Newport), Campylobacterjejuni, Shigella dysenteriae, Legionella pneumophila, Neisseriagonorrhoeae, and Vibrio species (such as V. cholerae, V. vulnificus, V.parahaemolyticus). Exemplary Gram-positive bacteria that can be killedusing the antimicrobial compositions provided herein include, but arenot limited to: Bacillus anthracis, Staphylococcus aureus (e.g.,methicillin resistant S. aureus), Enterococcus species (such asvancomycyin resistant Enterococci), Listeria monocytogenes, Clostridiumspecies (e.g., Clostridium difficile, Clostridium perfringens),pneumococcus, gonococcus, and streptococcal meningitis. Exemplary Acidfast bacteria that can be killed using the antimicrobial compositionsprovided herein include, but are not limited to Mycobacterium species(such as Mycobacterium tuberculosis, members of the Mycobacterium aviumcomplex [MAC]). In one example, the bacteria killed with the disclosedmethods is one or more of the following: Group A Streptococcus; Group BStreptococcus; Helicobacter pylori; Methicillin-resistant Staphylococcusaureus; Vancomycin-resistant enterococci; Clostridium difficile; E. coli(e.g., Shiga toxin producing strains); Listeria; Salmonella;Campylobacter; B. anthracis (such as spores); Chlamydia trachomatis; andNeisseria gonorrhoeae.

Viruses that can be killed using the disclosed methods include bothenveloped and non-enveloped positive-strand RNA viruses andnegative-strand RNA viruses.

Exemplary positive-strand RNA viruses include, but are not limited to:Picornaviruses (such as Aphthoviridae [for examplefoot-and-mouth-disease virus (FMDV)]), Cardioviridae; Enteroviridae(such as Coxsackie viruses, Echoviruses, Enteroviruses, andPolioviruses); Rhinoviridae (Rhinoviruses)); Hepataviridae (e.g.,Hepatitis A viruses); Hepeviridae (such as Hepatitis E virus);Togaviruses (examples of which include rubella; alphaviruses (such asWestern equine encephalitis virus, Eastern equine encephalitis virus,and Venezuelan equine encephalitis virus)); Astroviridae (such asAstroviruses), Flaviviruses (examples of which include Dengue virus,West Nile virus, and Japanese encephalitis virus); Calciviridae (whichincludes Norovirus and Sapovirus); and Coronaviruses (examples of whichinclude the MERS coronavirus and the SARS coronaviruses, such as theUrbani strain). Exemplary negative-strand RNA viruses include, but arenot limited to: Orthomyxyoviruses (such as the influenza virus),Rhabdoviruses (such as Rabies virus), and Paramyxoviruses (examples ofwhich include measles virus, respiratory syncytial virus, andparainfluenza viruses).

Viruses also include double-stranded RNA viruses. Double stranded RNAviruses that can be killed using the antimicrobial compositions providedherein include, but are not limited to Reoviridae (such as theRotaviruses).

Viruses also include DNA viruses. DNA viruses that can be killed usingthe antimicrobial compositions provided herein include, but are notlimited to: Herpesviruses (such as Varicella-zoster virus, for examplethe Oka strain; cytomegalovirus; and Herpes simplex virus (HSV) types 1and 2); Hepadnaviridae (such as Hepatitis B virus); Adenoviruses (suchas Adenovirus type 1, Adenovirus type 40, and Adenovirus type 41);Poxviruses (such as Vaccinia virus); and Parvoviruses (such asParvovirus B19).

Another group of viruses includes Retroviruses. Examples of retrovirusesthat can be killed using the antimicrobial compositions provided hereininclude, but are not limited to: human immunodeficiency virus type 1(HIV-1), such as subtype C; HIV-2; equine infectious anemia virus;feline immunodeficiency virus (FIV); feline leukemia viruses (FeLV);simian immunodeficiency virus (SIV); and avian sarcoma virus.

In one example, the virus killed with the disclosed antimicrobialcompositions is one or more of the following: HIV (for example an HIVantibody, p24 antigen, or HIV genome); Hepatitis A virus (for example anHepatitis A antibody, or Hepatitis A viral genome); Hepatitis B (HB)virus (for example an HB core antibody, HB surface antibody, HB surfaceantigen, or HB viral genome); Hepatitis C (HC) virus (for example an HCantibody, or HC viral genome); Hepatitis D (HD) virus (for example an HDantibody, or HD viral genome); Hepatitis E virus (for example aHepatitis E antibody, or HE viral genome); a respiratory virus (such asinfluenza A & B, respiratory syncytial virus, human parainfluenza virus,or human metapneumovirus), or West Nile Virus.

Protozoa, nematodes, and fungi are also types of microorganisms that canbe killed using the antimicrobial compositions provided herein.Exemplary protozoa include, but are not limited to, Plasmodium (e.g.,Plasmodium falciparum malaria), Leishmania, Acanthamoeba, Balmuthiamandrillaris, Giardia, Entamoeba, Cryptosporidium, Isospora,Balantidium, Trichomonas, Trypanosoma (e.g., Trypanosoma brucei,Trypanasoma cruzii), Naegleria fowleri, and Toxoplasma. Exemplary fungiinclude, but are not limited to: Saccharomyces, Candida albicans,Coccidiodes immitis, Stachybotrys chartarum, Blastomyces dermatitidis,and mildews.

In one example, bacterial spores are killed using the antimicrobialcompositions provided herein. For example, the genus of Bacillus andClostridium bacteria produce spores that can be killed with thedisclosed antimicrobial compositions. Thus, C. botulinum, C. difficile,C. perfringens, B. cereus, and B. anthracis spores can be killed. Inother examples, viable, but non-culturable bacteria are killed.

EXAMPLES

The following examples are provided to illustrate certain particularfeatures and/or embodiments. These examples should not be construed tolimit the disclosure to the particular features or embodimentsdescribed.

Example 1 Quillaja Saponin for Improving Solubility of Plant EssentialOils in Produce Wash Water Introduction

The consumption of organic produce has increased in recent years due tohealth concerns from consumers. The increased demand for fresh producemay raise the risk of foodborne illness outbreaks owing to theconsumption of contaminated produce. Better control measures are neededto prevent outbreaks as well as food spoilage, and to increase theshelf-life of fresh produce. Post-harvest treatment with sanitizers isan effective way to reduce pathogenic and background microorganisms. Toreduce the costs associated with post-harvest washing, a common practicein the produce industry is to reuse the wash water. In previous labscale tests, natural antimicrobials and organic sanitizers such asoregano oil and Chico Wash have shown antimicrobial activities againstS. Newport on organic leafy greens during recycling. Plant essentialoils are insoluble in water due to their hydrophobic properties.Improving their solubility in produce wash water will help enhance theantimicrobial activity. Various materials can be added in the wash waterto improve their solubility. Saponins are known for their foamingproperties and detergent-like activities which helps improve thesolubility of essential oils. Saponins could act as natural detergentsresulting in an emulsion of essential oil in water.

The addition of saponins at low concentrations with vigorous agitationhelped form a stable emulsion of essential oil in water. The objectiveof the present study was to investigate the effect of saponin onimproving the solubility of oregano oil and lemongrass oil in producewash water, thereby increasing bacterial reduction on organic babyspinach in a large scale test. The wash water was also recycled fivetimes and the efficacy of the plant antimicrobials investigated.

Materials and Methods

Bacterial strains used: For lab scale testing, S. Newport was used. Forlarge scale testing, non-pathogenic Escherichia coli K-12 ATCC 25253(streptomycin resistant; permitted to be handled in biosafety level 2labs in large volumes) was used. This strain has been commonly used inthe microbiology research field as a surrogate for E. coli O157:H7 andSalmonella.

Produce and Sanitizer: Organic baby spinach was obtained from a farm inMaricopa, Ariz. For large scale testing the following microemulsionswere prepared in the produce wash water and tested: oregano oil (0.3%)combined with quillaja saponin (0.005%), Chico Wash (1:20) combined withsaponin (0.005%), and 0.125% lemongrass oil or 0.1% oregano oil. Tapwater was used to make the microemulsion solutions and the mixtures wereshaken with vigorous agitation. Tap water, 50 ppm chlorine, and 3%hydrogen peroxide were also used as controls. For lab scale testing,0.3% oregano oil suspended in PBS without saponin was used, and PBS wasused as a control.

Sample preparation and inoculation: For lab scale testing, baby spinachsamples were rinsed with deionized (DI) water three times. Ten grams ofbaby spinach were weighed for each sample. Samples were exposed to UVlight in a biohood for 30 minutes. Each sample was immersed in 200 mL of10⁶ CFU/mL Salmonella Newport culture for 2 minutes, and dried in abiohood for 30 minutes. Oregano oil (0.9 mL) was added into 300 mL ofPBS to make 0.3% solutions. The solutions were stomached for 1 minute tomix well. The solutions were chilled to 10° C. in ice water bath.

For large scale testing, each sample consisted of 5 kilograms of babyspinach. E. coli K-12 overnight culture (40 mL) was added into 40 L ofBuffered Peptone Water (BPW) to make an inoculum (ca. 10⁶ CFU/mL). Eachsample was inoculated by immersion, agitated for 2 minutes and dried ina biohood for 1 hour. Five samples were prepared for each sanitizertest. Positive control samples were taken after the spinach samples weredried in the biohood.

Reuse of natural antimicrobials and sanitizer to reduce bacteria on babyspinach: For lab scale testing, three spinach samples were immersed inthe 0.3% oregano oil solution for 2 minutes with gentle agitation.Samples were taken out from the solution and put into stomacher bag andstored at 4° C. The same solutions were used for four more treatmentswith new spinach samples. The solutions were chilled to 10° C. beforeeach treatment. PBS was used as a control.

For large scale testing, to simulate the commercial scale washingprocess, a large stainless steel tank (109×51×41 cm) was used forspinach washing. Seventy-five liters of wash water was added into thetank. For the washes with oregano oil or lemongrass oil, the oil wasadded into the wash water with saponin and agitated vigorously with asnow shovel for 5 minutes. Baby spinach samples (5 kg each) wereimmersed in the solution and agitated for 2 minutes. The wash water wasused five times to treat five different batches of baby spinach samplesone after another. After each wash, spinach samples were taken toenumerate the surviving E. coli K-12 population. Experiments were alsoconducted using tap water, 50 ppm chlorine, and 3% hydrogen peroxidetreatments using the same protocol. Survivors of E. coli K-12 wereenumerated on baby spinach and in wash water after each wash.

Enumeration of surviving bacteria on baby spinach: For lab scaletesting, spinach samples were taken at day 0, 1, and 3 to enumerate S.Newport survivors on the leaves. BPW (90 mL) was added into thestomacher bag containing 10 g spinach sample, and stomached at normalspeed for 1 minute. Serial dilutions were made in 0.1% peptone water andplated on xylose lysine desoxycholate (XLD) agar. The XLD plates wereincubated at 37° C. for 24 hours. The colonies on the plates werecounted for the enumeration of surviving S. Newport cells.

For large scale testing, after each wash treatment, fifteen spinachsamples (25 g each) were weighed and stored in stomacher bags. Fivesamples among these were plated at day 0. The other ten samples werestored at 4° C. and plated for enumeration on day 1 and day 3 (fivesamples for each day). For enumeration, 225 ml of BPW was added into thestomacher bag containing 25 g of spinach samples, and stomached atnormal speed for 1 minute. Serial dilutions were made in 0.1% peptonewater and plated on Eosin-methylene blue (EMB) agar plates with 300μg/ml of streptomycin. The EMB plates were incubated at 37° C. for 24hours. The colonies on the plates were counted for the enumeration ofsurviving E. coli K-12 cells.

Results

Survival of S. Newport on spinach after 0.3% oregano oil treatmentwithout saponin: Table 2 shows the surviving S. Newport population onspinach samples after 0.3% oregano oil treatment in the lab scaletesting. At day 0, the first wash reduced Salmonella population to belowdetection limit, and the 2nd to 5th washes caused 1.4-2.2 logreductions. At both days 1 and 3, Salmonella was not detected on samplesfrom the first washes, and the 2nd to 5th washes caused 1.2-2.4 and1.4-2.2 log reductions for day 1 and 3, respectively.

TABLE 2 Survival of S. Newport on organic baby spinach (Log CFU/g) after0.3% oregano oil treatments (without saponin) Day 0 Day 1 Day 3 0.3%oregano oil 1st wash <1.00 ± 0.00  <1.00 ± 0.00  <1.00 ± 0.00  2nd wash2.05 ± 0.91 1.83 ± 0.75 1.86 ± 0.88 3rd wash 2.60 ± 0.67 2.78 ± 0.232.77 ± 0.14 4th wash 2.84 ± 0.35 2.78 ± 0.42 2.74 ± 0.36 5th wash 2.96 ±0.56 3.16 ± 0.31 2.82 ± 0.06 PBS control 1st wash 4.11 ± 0.06 4.40 ±0.15 4.06 ± 0.20 2nd wash 4.23 ± 0.02 4.25 ± 0.14 4.10 ± 0.27 3rd wash4.31 ± 0.21 4.29 ± 0.07 4.09 ± 0.10 4th wash 4.34 ± 0.15 4.27 ± 0.184.20 ± 0.15 5th wash 4.34 ± 0.14 4.32 ± 0.08 4.20 ± 0.36

Survival of E. coli K-12 on spinach after 0.3% oregano oil and saponintreatment: Table 3 shows the surviving population on spinach after 0.3%oregano oil and saponin treatment in the large scale testing. At day 0,the 1st and 2nd washes reduced the E. coli population to below detectionlimit, and the 3rd to 5th washes showed 3.3-1.1 log reductions. At day 1and 3, the 1st, 2nd and 3rd washes reduced E. coli population to belowdetection limit. The 4th and 5th washes showed 2.6-1.7 and 4.3-1.2 logreduction at days 1 and 3, respectively.

TABLE 3 Survival of E. coli K-12 on spinach samples (Log CFU/g) after 5washes in 0.3% oregano oil with 0.005% saponin E.coli K-12 population onspinach Sample Day 0 Day 1 Day 3 Positive 4.60 ± 0.11  5.90 ± 0.11  5.67± 0.32 1st wash <1.00 ± 0.00  <1.00 ± 0.00 <1.00 ± 0.00 2nd wash <1.00 ±0.00  <1.00 ± 0.00 <1.00 ± 0.00 3rd wash 1.34 ± 0.28 <1.00 ± 0.00 <1.00± 0.00 4th wash 2.56 ± 0.26  3.25 ± 0.51  1.38 ± 0.85 5th wash 3.46 ±0.11  4.18 ± 0.11  4.45 ± 0.16 Data are shown as mean ± SD, n = 5

Survival of E. coli K-12 on spinach after Chico Wash combined withessential oil and saponin treatment: Table 4 shows the survivingpopulation on spinach after pH 2.4 Chico wash combined with 0.125%lemongrass oil and saponin treatment in the large scale testing. At day0, the 1st wash caused 2 log reductions in E. coli population, and the2nd to 5th washes showed 1.6-1.1 log reductions. At day 1 and 3, the 1stwash reduced E. coli population to below detection limit. The 2nd to 5thwashes showed 1.7-1.4 and 1.8-1.2 log reduction at day 1 and 3,respectively.

TABLE 4 Survival of E. coli K-12 (Log CFU/g) on spinach samples after 5washes in Chico Wash combined with 0.125% lemongrass oil and 0.005%saponin Day 0 Day 1 Day 3 Positive control 4.75 ± 0.10 4.63 ± 0.04 4.38± 0.26 1st wash 2.76 ± 0.20 <1.00 ± 0.00  <1.00 ± 0.00  2nd wash 3.20 ±0.12 2.97 ± 0.09 2.60 ± 0.28 3rd wash 3.39 ± 0.18 3.02 ± 0.07 2.65 ±0.23 4th wash 3.53 ± 0.07 3.14 ± 0.13 2.68 ± 0.16 5th wash 3.62 ± 0.163.24 ± 0.10 3.20 ± 0.11 Data are shown as mean ± SD, n = 5

Table 5 shows the surviving population on spinach after pH 2.4 Chicowash combined with 0.1% oregano oil and saponin treatment in the largescale testing. At day 0, the 1st wash caused 2.1 log reductions in E.coli population, and the 2nd to 5th washes showed 1.5-1.4 logreductions. At day 1 and 3, the 1st wash reduced E. coli population tobelow detection limit. The 2nd to 5th washes showed 1.8-1.3 and 1.7-1.0log reduction at day 1 and 3, respectively.

TABLE 5 Survival of E. coli K-12 on spinach samples (Log CFU/g) after 5washes in pH 2.4 Chico Wash with 0.1% oregano oil and 0.005% saponin E.coli K-12 population on spinach Sample Day 0 Day 1 Day 3 Positivecontrol 4.95 ± 0.05 4.22 ± 0.22 4.19 ± 0.20 1st wash 2.84 ± 0.09 <1.00 ±0.00  <1.00 ± 0.00  2nd wash 3.42 ± 0.10 2.47 ± 0.18 2.65 ± 0.22 3rdwash 3.54 ± 0.06 2.73 ± 0.06 2.66 ± 0.11 4th wash 3.56 ± 0.10 2.64 ±0.22 2.53 ± 0.23 5th wash 3.56 ± 0.19 2.89 ± 0.18 3.15 ± 0.19 Data areshown as mean ± SD, n = 5

Survival of E. coli K-12 on spinach after re-using tap water, wash watercontaining 50 ppm chlorine and wash water containing 3% hydrogenperoxide for washing five batches of baby spinach: Tap water, 50 ppmchlorine and 3% hydrogen peroxide are commonly used in organic produceindustry, so we included them as controls in this study. The survival ofE. coli K-12 on spinach after these treatments in the large scaletesting is shown in Tables 6-8. For tap water treatments (Table 6),there were 0.9-1.1 log reductions in E. coli K-12 population at day 0,while only 0.1-1.0 and 0.7-0.8 log reductions were observed at day 1 and3, respectively.

TABLE 6 Survival of E. coli K-12 on spinach samples (Log CFU/g) after 5washes in tap water E. coli K-12 population on spinach Sample Day 0 Day1 Day 3 Positive control 4.87 ± 0.03 4.60 ± 0.08 4.33 ± 0.24 1st wash3.87 ± 0.11 3.73 ± 0.05 3.56 ± 0.08 2nd wash 3.92 ± 0.04 3.64 ± 0.103.49 ± 0.10 3rd wash 3.85 ± 0.07 3.84 ± 0.02 3.56 ± 0.04 4th wash 3.84 ±0.44 4.46 ± 1.30 3.66 ± 0.06 5th wash 3.77 ± 0.11 3.84 ± 0.05 3.63 ±0.03 Data are shown as mean ± SD, n = 5

Table 7 shows the results from 50 ppm chlorine treatment. During 1st to5th washes with 50 ppm chlorine, 1.1-1.6 log reduction was observed atday 0; 0.7-1.0 and 0.5-0.7 log reductions were observed at day 1 and 3,respectively.

TABLE 7 Survival of E. coli K-12 on spinach samples (Log CFU/g) after 5washes in 50 ppm chlorine E. coli K-12 population on spinach Sample Day0 Day 1 Day 3 Positive 4.81 ± 0.10 4.26 ± 0.23 3.99 ± 0.12 1st wash 3.25± 0.14 3.57 ± 0.04 3.30 ± 0.11 2nd wash 3.47 ± 0.07 3.42 ± 0.11 3.40 ±0.08 3rd wash 3.39 ± 0.10 3.40 ± 0.13 3.28 ± 0.07 4th wash 3.57 ± 0.203.38 ± 0.13 3.37 ± 0.06 5th wash 3.67 ± 0.11 3.29 ± 0.14 3.46 ± 0.15Data are shown as mean ± SD, n = 5

Similar to Chico Wash and 50 ppm chlorine treatments on spinach samples,hydrogen peroxide caused 0.8-1.2 log reduction at day 0. There were1.0-1.3 log reduction for both day 1 and day 3. (Table 8).

TABLE 8 Survival of E. coli K-12 on spinach samples (Log CFU/g) after 5washes in 3% hydrogen peroxide E. coli K-12 population on spinach SampleDay 0 Day 1 Day 3 Positive 4.56 ± 0.21 4.87 ± 0.17 4.83 ± 0.09 1st wash3.74 ± 0.08 3.58 ± 0.14 3.69 ± 0.05 2nd wash 3.58 ± 0.16 3.76 ± 0.303.54 ± 0.10 3rd wash 3.36 ± 0.28 3.83 ± 0.17 3.84 ± 0.14 4th wash 3.76 ±0.14 3.66 ± 0.19 3.67 ± 0.18 5th wash 3.37 ± 0.29 3.62 ± 0.16 3.74 ±0.02 Data are shown as mean ± SD, n = 5

Comparison of bacterial log reductions on spinach among varioussanitizers: Table 9 shows the log reductions on spinach samples after 5washes with various sanitizers tested in this study. Tap water treatmentshowed up to 1.1 log reduction at day 0, but there were only 0.7-0.8 logreduction at day 3. Compared to chlorine and hydrogen peroxide, 0.3%oregano oil with or without saponin, pH 2.4 Chico Wash combined with0.125% lemongrass oil or 0.1% oregano oil and saponin showed bettereffects in reducing bacterial population on spinach samples: the 0.3%oregano oil with saponin caused the highest reductions at day 0 (3.6log), 1 (4.9 log) and 3 (4.7 log). The 0.3% oregano oil with saponinshowed greater log reductions than the 0.3% oregano oil without saponin

TABLE 9 Bacterial reductions (Log CFU/g) on spinach samples aftersanitizer treatments Day 0 Day 1 Day 3 Tap water 0.9-1.1 0.1-1.0 0.7-0.850 ppm chlorine 1.1-1.6 0.7-1.0 0.5-0.7 3% hydrogen peroxide 0.8-1.21.0-1.3 1.0-1.3 pH 2.4 Chico Wash with 1.1-2.0 1.4-3.6 1.2-3.4 0.125%lemongrass oil and saponin pH 2.4 Chico Wash with 0.1% 1.4-2.1 1.3-3.21.0-3.2 oregano oil and saponin 0.3% oregano oil with saponin 1.1-3.61.7-4.9 1.2-4.7 0.3% oregano oil without 1.4-3.1 1.2-3.4 1.4-3.1 saponin

Conclusion

Among all the solutions tested, the 0.3% oregano oil with 0.005% saponinmicroemulsion showed the greatest bacterial reduction at day 0, 1 and 3.The 0.3% oregano oil with saponin caused greater bacterial logreductions than the same concentration of oregano oil without saponin.The results showed an improvement in bacterial reduction due to theaddition of Quillaja saponin.

Example 2 Ozonized Water with Plant Antimicrobials Inactivates BacteriaIntroduction

The use of plant antimicrobial combinations along with ozone has severaladvantages. The use of Quillaja saponins and olive extracts could helpin better dispersion of the essential oils in water. While both oliveextract and oregano oil have demonstrated antimicrobial activity againstfoodborne pathogens on organic leafy green surfaces, the combinations ofthese compounds with ozonized water could present multiple hurdles tobacterial pathogens and result in increased antimicrobial activity. Theobjective of this study was to evaluate the efficacy of ozone incombination with plant extracts, essential oils and their activecomponents in reducing Salmonella population on iceberg lettuce leaves.

Materials and Methods

Bacterial culture: Salmonella enterica serovar Newport SN78 (bovineisolate; provided by Dr. Marilyn Erickson, University of Georgia,Griffin, Ga.) was used for this experiment. Dual antibiotic resistance(100 μg/ml ampicillin and 25 μg/ml streptomycin, Amresco, Solon, Ohio)was developed in the strain through incremental antibiotic exposure. Theantibiotic resistance pattern of this strain provided efficienttraceability in soil and composts and the strain had growth ratecomparable to that of the parent strain. The frozen stock culture wasinitially revived through two transfers into brain heart infusion broth(BHIB) (Becton, Dickinson and Co (BD), Sparks, Md.) followed byisolation on xylose lysine desoxycholate (XLD) agar (Becton, Dickinsonand Co (BD), Sparks, Md.) containing 100 μg/ml ampicillin and 25 μg/mlstreptomycin.

Inoculum Preparation: For each experiment, a 20 hour overnight culturewas prepared by inoculating 100 μl of the culture in 30 ml of trypticsoy broth (TSB) containing 100 μg/ml ampicillin and 25 μg/mlstreptomycin and incubating at 37° C. in a desktop orbital shaker at 200rpm (MaxQ 4450, Thermo Scientific, Dubuque, Iowa, USA). The cells in themedium were pelleted by centrifugation at 4000 g (Eppendorf Model 5810,Hamburg, Germany) and the supernatant was discarded. The pellet waswashed in 20 ml phosphate buffered saline (PBS, Difco, Becton Dickinson,Sparks, Md.) twice and suspended in 180 ml of PBS in a sterile 1 Lstomacher bag (Nasco Whirl-Pak®, Fort Atkinson, Wis., USA) to obtain afinal concentration of approximately 6.5±1 log CFU/g.

Produce preparation and inoculation: Organic iceberg lettuce waspurchased from a local grocery store in Tucson, Ariz. The four outerleaves of the iceberg lettuce were removed and discarded. Whole leafsamples (10 g±0.5 g each) were used. The iceberg lettuce samples wereinoculated by immersing 10 g portions into the PBS-S. Newport suspensionfor 2 minutes. After immersion, the excess culture suspension wasallowed to drain from the leaf and the leaves were allowed to dry in abiohood for 1 hour to aid in the attachment of S. Newport to the leafsurface.

Antimicrobial wash solution preparation: The test plant-basedantimicrobials used in this study consisted of oregano oil made frompure Origanum vulgare (Lhasa Karnak Company, Berkeley, Calif.), itsactive component carvacrol (98% pure, molecular weight 150.2, CAS no.499-75-2, Sigma, St. Louis, Mo.), olive extract (CreAgri, Hayward,Calif.), and quillaja saponin made from Quillaja saponaria (SigmaAldrich, St. Louis, Mo.). Oregano oil (essential oil) was tested at a0.1% (v/v) concentration and its active component carvacrol atconcentrations of 0.1-0.5% (v/v). Olive extract was tested atconcentrations of 1 and 5%. Saponin was added at 0.0001%. All plantantimicrobials were prepared by mixing thoroughly in 2 L PBS.

Ozone equipment: Ozone gas was generated using an ozone generator(ForeverOzone™ OG-5G-BB). The unit consisted of a 5 KV transformer, a 25LPM air pump, 110 CFM, 120 mm AC fan for cooling and a corona dischargegenerator producing 5000 mg/h of ozone. Ozone was generated into theproduce wash suspension using a modified sparger as described previously(Dev Kumar et al., Food Control 59:172-177, 2016). The “perforated tube”sparger consisted of Clear PVC tubing, 30 cm (Nalgene 180 clear plastictubing, I.D. ⅛ inch×O.D. 3/16 inch×Wall 1/32 inch, Nalgene Nunc Int.Corp; Rochester, N.Y.) that was perforated with a 12 gauge insulinsyringe (Walgreens, Tucson, Ariz.). Perforations were created throughoutthe tubing (100/cm). The ozone generator was connected to the perforatedtube sparger using a T connector (Thermo Scientific, Hudson, N.H.).

Ozone measurement: Residual ozone in wash waters was measured using aspectrophotometer (Spectronic 200, Thermo Fisher Scientific, Waltham,Mass.) for a concentration range of 0.01 to 0.1 mg O₃/L using the IndigoColorimetric Method (Standard methods for the examination of waters andwaste waters, 20th edition) (APHA, 2005). Briefly, 10 ml of Indigoreagent 1 (20 ml potassium indigo trisulfonate stock solution, 10 gsodium dihydrogen phosphate, 7 ml concentrated sulfuric acid) was addedto two sterile 100 ml measuring cylinders. The ozonized water was addedto one cylinder and regular deionized water was added to the blankcylinder. The absorbance difference was measured between the twosolutions at 600 nm to determine ozone content in the aqueous form.

Ozone-plant antimicrobial Treatment: The 2 L aliquot ofPBS-antimicrobial suspension was placed in a 5 L sterile stomacher bag.The bag was cooled to a temperature of 1-4° C. using a combination ofice and dry ice for the entire duration of the ozonation treatment. Thewater was chilled to promote better retention of ozone in the aqueousphase (Dev Kumar et al., Food Control 59:172-177, 2016). The perforatedozone sparger was placed at the bottom of the bag and the water wascirculated using an aquarium pump (Top Fin® Power Head 50, PetSmart,Tucson, Ariz.) for better dispersion of the ozone molecules andsuspension of the oils. Ozone was introduced into the wash suspensionfor 30 minutes before leaf treatment. Leaf treatments were performed for60, 90 and 120 minutes when the wash water suspension containedindividual plant antimicrobials (oregano oil, olive extract) and for 60and 90 minutes when carvacrol was used. When combinations of plantantimicrobials with saponin were evaluated, ozonation was carried outfor a duration of 20 minutes.

Microbiological analysis: Leaf samples were collected immediately aftertreatment for the enumeration of surviving Salmonella. Leaf samples (10g) were pummeled in the stomacher at normal speed (230 rpm) in 90 ml BPWfor 1 min. Enumeration of survivors following treatment was carried outby spread plating the serially diluted above-mentioned suspensions onXLD agar containing 100 μg/ml ampicillin, and 25 μg/ml streptomycin. Theplates were incubated at 37° C. for 24 hours and the Salmonella colonieswere counted.

Statistical Analysis: All ozone-plant antimicrobial combinationtreatments of iceberg lettuce leaves were carried out in triplicate. Theexperiment for the studies was a randomized blocked design factorialtreatment arrangement, repeated measures with sampling, blocked onreplication. Means were separated using Least Square Means using JMP®Pro version 11 (SAS Institute, Inc., Cary, N.C.). Significantdifferences are defined at p<0.05

Results

Iceberg lettuce leaf treatment with ozone: Immersion of S. Newportcontaminated iceberg lettuce leaves in ozonized water resulted in adecrease of 1.76±0.27, 1.67±0.28, and 2.09±0.54 Log CFU/g in S. Newportpopulation after 60, 90 and 120 min of exposure, respectively (FIG. 1).The concentration of ozone in water reached 0.17±0.04, 0.18±0.04, and0.23±0.07 mg/L at 60, 90, and 120 min, respectively.

Iceberg lettuce leaf treatment with ozone-saponin: Quillaja saponin(0.0001%) did not exhibit bactericidal activity against S. Newport oniceberg lettuce leaves over a 20 minute duration when used individually.The use of the ozone-quillaja saponin combination reduced the populationof S. Newport on iceberg lettuce leaves by 1.24±0.44 log CFU/g after 20minutes of treatment (FIG. 2). The addition of saponin to the wash waterresulted in the quenching of ozone and a reduction in the concentrationof ozone below detectable limits.

Iceberg lettuce leaf treatment with ozone-oregano oil combination:Treating iceberg lettuce leaves with ozone in combination with 0.1%(v/v) oregano oil resulted in reductions of 4.14±1.8, 3.42±1.74, and3.08±1.57 log CFU/g after 60, 90, and 120 min exposure, respectively(FIG. 1) and resulted in a significant decrease in S. Newportpopulations at the end of the treatment durations in comparison to theinitial population (p<0.05). An increase in treatment duration did notresult in increased antimicrobial activity. Use of ozone+0.5% oreganooil combination resulted in reduction of S. Newport population to belowthe limit of detection (10 CFU/g) from an initial population of 6.39±0.5log CFU/g (FIG. 1) after 60 minutes of treatment (p<0.05), indicatingthat the concentration of oregano oil significantly affected theantimicrobial efficacy of the treatment. Addition of oregano oil to theozonized water affected the ability to determine changes in absorptionof indigo reagent because of color change of water and the possiblequenching of residual ozone.

Iceberg lettuce leaf treatment with ozone-olive extract combinations:Treatment of iceberg lettuce with ozone and olive extract combinationswas performed for durations of 60, 90 and 120 minutes. Theconcentrations of olive extract used for the combination wash with ozonewere 1% and 5%. The use of 1% olive extract resulted in a decrease in S.Newport population on iceberg lettuce leaves by 2.54±0.79, 2.48±0.28,and 2.23±0.45 log CFU/g (p<0.05) after 60, 90, and 120 minutes,respectively (FIG. 1). The use of 5% olive extract in combination withozone for 60, 90, and 120 min resulted in a 3.64±1.57, 3.57±1.3, and4.2±1.57 log CFU/g reduction (p<0.05) of S. Newport on iceberg lettuce,respectively (FIG. 1). The concentration of olive extract used affectedthe efficacy of the treatment, as 5% resulted in more S. Newportreduction than 1%. The combined use of quillaja saponin, olive extract(1%), and ozone for washing iceberg lettuce for a duration of 20 minutesresulted in a 3.24±0.58 log CFU/g (p<0.05) decrease in S. Newportpopulation on iceberg lettuce leaf (FIG. 2). A plant antimicrobialcombination ozone wash containing quillaja saponin, olive extract (1%),and oregano oil (0.1%) for a duration of 20 minutes resulted in a3.27±0.53 log CFU/g reduction in S. Newport population (p<0.05) (FIG.2).

Iceberg lettuce leaf treatment with ozone-carvacrol combinations:Combination treatments of ozone with carvacrol were performed for 60 and90 minutes. The concentrations of carvacrol used were 0.1%, 0.3%, and0.5%. The use of carvacrol in combination with ozone at all threeconcentrations and both treatment times resulted in reduction of S.Newport populations to levels below detection. The use of 0.1, 0.3, and0.5% carvacrol in combination with ozone for 60 minutes resulted inreductions of 5.11±0.38, 5.99±0.52, and 7.29±0.32 log CFU/g of S.Newport, respectively. The use of 0.1, 0.3, and 0.5% carvacrol incombination with ozone for 90 minutes resulted in reductions of6.34±1.69, 6.55±1.3, and 7.54±0.21 log CFU/g S. Newport, respectively.

Discussion

The present study involved the use of ozonized water in combination withoregano oil, olive extract, carvacrol, and saponins against S. Newport.An isolate from bovine origin was chosen, as leafy greens can becontaminated by cattle feedlot run-off and contact with manure. Previousresearch with aqueous ozone washing of leafy greens have indicated mixedoutcomes. The washing of cilantro leaves with ozonized water did notdecrease total plate counts after treatment (Wang et al., Food Res. Int.37:949-956, 2004), while exposing shredded lettuce to aqueous ozone for3 minutes resulted in decreased counts of mesophilic and psychrotrophicbacteria by 1.4 and 1.8 log CFU/g, respectively (Kim et al., J. FoodSafety 19:17-34, 1999). Research with plant compounds has indicated thatantimicrobial activity could be dose dependent. The use of 5% and 1%olive extract resulted in 1.7 and 1.4 Log CFU/g reduction in S. Newportpopulation, respectively, on iceberg lettuce (Moore et al., J. FoodProt. 74; 1676-1683, 2011). While the use of oregano oil at 0.1% forwashing iceberg lettuce resulted in <1 log reduction, the use of 0.5%resulted in over 5 log reduction of S. Newport (Moore-Neibel et al.,Food Microbiol. 34(1):123-129, 2012). Hence in the studies describedherein, plant-based antimicrobials such as oregano oil, olive extract,and quillaja saponin were tested at low concentrations in combinationwith ozone to determine if there was any improvement over previouslyreported levels of bacterial reduction when individual components wereused.

The long durations of treatments used in this study are notrepresentative of washing practices used for individual batches in theindustry, but these mimic the durations for which wash water is reusedby replenishing free chlorine. Practices such as hydrocooling usuallyresult in longer contact of produce with water, to lower the temperatureof produce. Hence, the use of ozone and plant based antimicrobials canhave applications in both washing and hydrocooling practices wheneffective concentrations of plant based antimicrobials are used. The useof ozone in combination with carvacrol (0.1%, 0.3% and 0.5%) and 0.5%oregano oil exhibited a reduction in S. Newport to below levels ofdetection (10 CFU/g) from initial populations exceeding 6 logs CFU/g.Earlier investigations in our laboratory with carvacrol resulted in over5 log CFU/g reduction of S. Newport on iceberg lettuce at concentrationof 0.3 and 0.5%, but not at 0.1%. Treatments in which ozone andcarvacrol (0.3 and 0.5%) were used in combination resulted in nosurvivors of the pathogen. Previous work performed using only 0.3 and0.5% carvacrol resulted in over 5 log CFU/g reduction (no survivorsdetected) of S. Newport as well, indicating that ozone might not havecontributed to the decrease of S. Newport when carvacrol was used atthese concentrations. Evidence of additional antimicrobial efficacybetween carvacrol and ozone can be ascertained when 0.1% carvacrol wasused in combination with ozone, as this treatment resulted in over 5 logCFU/g reduction, while the use of only 0.1% carvacrol resulted in 1 logCFU/g reduction.

Oregano oil has demonstrated significant antimicrobial activity againstfoodborne pathogens in a concentration dependent manner (Moore-Neibel etal., Food Microbiol. 34(1):123-129, 2012). In this study, it wasobserved that the use of 0.1% oregano oil had a protective effect onSalmonella and might have even resuscitated cells injured by theoxidative damage caused by ozone. This observation is supported by anincrease in S. Newport survival on iceberg lettuce (FIG. 1) after longertreatment durations of 90 and 120 minutes, in comparison to 60 minutes.

An average concentration of 0.2 mg/L of ozone was measured in the washwater at the end of treatments. Ozone gas was delivered throughout thetreatment duration to compensate for loss of aqueous ozone due toquenching by organic matter, off gassing and relatively short half-lifeof the ozone molecule. Organic matter consumes ozone and may competewith microorganisms, reducing the efficacy of ozone (Guzel-Seydim etal., LWT-Food. Sci. Tech. 37:453-460, 2004; Khadre et al., J. Food. Sci.66:1242-1252, 2001; Kim et al., J. Food Prot. 62:1071-1087, 1999),hence, requiring continuous reintroduction of ozone into wash waters.Aqueous ozone was not detected in water containing oregano oil, oliveextract, and saponins due to the possible quenching of the ozonemolecule and the change in water color that affected the absorbance ofthe indigo reagent that was essential for measuring the dissolved ozone.

Saponin resulted in no antimicrobial activity against S. Newport whentested individually, and olive extract resulted in <2 Log CFU/greductions in S. Newport. These reductions were lower in comparison tothose obtained in treatments where ozone was used in combination withantimicrobials, indicating that the combination of ozone with plantbased antimicrobials resulted in enhanced antimicrobial activity againstS. Newport. The combination of 0.0001% saponin, 1% olive extract, and0.1% oregano oil resulted in excess of 4 log CFU/g reduction of S.Newport within 20 minutes, though the treatments also resulted insignificant foam formation, contributing to lowered treatment timeselection than other treatments. While chlorination could result inpitting or corrosion of equipment and presence of carcinogenicbyproducts, the use of quillaja saponin could be advantageous because ofits detergent-like nature, which could result in reduced attachmentstrength of pathogenic bacteria to equipment surfaces. Hence, use ofozone in combination with plant antimicrobials could be an effectivepost-harvest processing step for the iceberg lettuce industry, as noneof the treatments used in this study affected the appearance of iceberglettuce by visual observation.

Example 3 Control of Biofilm Formation on Food Contact Surfaces

Evaluation of Biofilm Formation by Salmonella enterica and Listeriamonocytogenes on Five Different Food Contact Surfaces

A protocol based on crystal violet staining was evaluated for testingthe biofilm forming abilities of two foodborne pathogens—Salmonellaenterica and Listeria monocytogenes—on five different food contactsurfaces: stainless steel, high density polyethylene (HDPE), polyvinylchloride (PVC), polycarbonate (PC) and Buna-N rubber. Ten milliliters(ml) of diluted TSB (1:10 v/v) inoculated with 7 log CFU/ml of one ofthe test bacterial cultures (S. enterica or L. monocytogenes) was addedto the food contact surface coupons. The control was autoclaved tapwater. These coupons were incubated at room temperature for up to threedays. After 14 hours, the coupons were rinsed in 25 ml of steriledeionized water to remove the planktonic cells and fresh TSB (diluted1:10 v/v; without any bacteria) was added as a source of nutrients.Every 14 hours the coupons were rinsed to remove the planktonic cellsand fresh diluted TSB (1:10 v/v) added. Samples were taken at days 0, 1,and 3. The coupons were rinsed in 25 ml of sterile deionized water toremove planktonic cells. The coupons were air dried, and 5 ml of crystalviolet (0.1% w/v) was added and incubated at room temperature (22° C.)for 45 minutes. The dye was aspirated and the coupons were rinsed in 25ml of sterile de-ionized water and air dried for 1 hour in a biohoodfollowing which 5 ml of 95% ethanol was added to dissolve the dye boundto the biofilm. The coupons were agitated gently for 30 minutes todissolve the crystal violet dye, following which 100 μl ethanol wastransferred to the wells of a 96-well plate. The amount of dissolved dyewas quantified at an absorbance of 600 nm using a microplatespectrophotometer and the OD₆₀₀ was measured using 95% ethanol as theblank. The OD values indicate the amount of bound crystal violet and theamount of biofilm formed. The results are shown in Table 10.

TABLE 10 OD₆₀₀ values of crystal violet dye from biofilm formation bySalmonella enterica and Listeria monocytogenes on various coupons BlankStainless Buna (95% Day Bacteria HDPE PVC PC steel N-rubber Ethanol) Day0 S. enterica 0.057 0.06 0.063 0.057 0.448 0.043 L. monocytogenes 0.0730.083 0.076 0.045 1.032 0.042 Control 0.068 0.059 0.062 0.048 0.9580.042 Day 1 S. enterica 0.548 1.234 0.548 0.77 3.253 0.04 L.monocytogenes 0.313 0.38 0.889 1.031 1.56 0.041 Control 0.079 0.0650.067 0.05 1.005 0.041 Day 3 S. enterica 1.913 1.621 1.536 1.208 3.8170.04 L. monocytogenes 1.494 2.573 1.656 1.773 3.667 0.044 Control 0.0640.086 0.065 0.052 0.865 0.041

A protocol based on direct plating was also evaluated for testing thebiofilm formation by Salmonella or L. monocytogenes. Biofilms wereformed on three different food contact surface coupons (HDPE, Buna-Nrubber, and 316 stainless steel) for up to 3 days in 35 mm mini-petridishes. Biofilms were formed using a 1:10 diluted TSB solution (10 mL)with either S. enterica or L. monocytogenes inoculum (100 μL). Thediluted TSB was changed every 16-18 hours with new 1:10 diluted TSB (10mL). Coupons were removed for sampling and enumeration of stronglyattached bacteria at three different time points (Day 0, 1, and 3). Thecoupons were rinsed with deionized water five times to remove planktoniccells. Then the coupons were immersed in 10 mL of BPW. The coupons weresonicated for 2 minutes using different settings (Tables 11 and 12) foreach organism. After sonication, the solution was serially diluted andplated on Tryptic Soy Agar (TSA). Plates were incubated at 37° C. for24-48 hours. The colonies were counted and the colony forming units weredetermined for the various sonication settings, so that the appropriatesetting with the most recovery could be determined. The results areshown in Tables 11 and 12. The results demonstrated that the sonicationsetting of 40:40 provided the best recovery for S. enterica, while thesetting of 40:60 provided the best recovery in case of L. monocytogenes.These settings were used in further experiments to recover the bacterialcells from coupons during sampling and enumeration (by spread plating)of the bacteria in biofilms.

TABLE 11 Bacterial population (Log CFU/mL) recovered from the biofilmsformed by Listeria monocytogenes on various food contact surface couponsDay Sonicator 316 stainless BuNa—N rubber HDPE Day 0 20:40 5.08 5.114.88 40:40 5.02 5.09 5.19 40:60 5.27 5.23 5.37 60:60 5.13 5.15 5.35 Day1 20:40 7.60 7.18 6.64 40:40 7.28 7.17 6.62 40:60 7.62 7.25 6.29 60:607.59 7.56 6.61 Day 3 20:40 7.52 7.74 7.20 40:40 7.63 7.57 6.81 40:607.48 7.84 6.83 60:60 7.61 7.58 7.02

TABLE 12 Bacterial population (Log CFU/mL) recovered from the biofilmsformed by Salmonella Newport on various food contact surface coupons DaySonicator 316 stainless BuNa—N rubber HDPE Day 0 20:20 5.44 5.13 4.3020:40 5.46 4.27 5.20 40:40 5.30 5.31 5.13 40:60 5.41 5.71 5.96 Day 120:20 7.16 7.00 6.80 20:40 7.15 7.10 6.93 40:40 7.07 7.06 7.02 40:606.77 7.04 6.97 Day 3 20:20 7.13 6.98 6.86 20:40 7.45 7.40 7.38 40:407.53 7.71 7.21 40:60 7.35 7.38 7.39

The results demonstrated that foodborne pathogenic bacteria evaluated(S. enterica and L. monocytogenes) can form biofilms on various producecontact surfaces such as stainless steel, HDPE, PVC, PC, and BunaN-rubber. The biofilms formed on these surfaces can be detected eitherby crystal violet staining or direct plating methods.

Reduction of Biofilm Formation on Food Contact Surfaces by NaturalSanitizers

The food contact surface coupons were immersed in plant extract,essential oil, and/or 0.0001% emulsifier (Quillaja saponin) for 30minutes. The coupons were removed from the solutions and inoculated withS. enterica or L. monocytogenes and the biofilm formation was evaluatedusing the crystal violet staining method described above. The OD valuesof the crystal violet solutions are shown in Tables 13-15. Variousconcentrations of oregano oil (0.5%, 0.7%, and 1.0%) with emulsifierwere also tested against S. enterica biofilm formation on food contactsurfaces (Table 16).

TABLE 13 OD6₀₀ values of crystal violet dye from biofilm formation onvarious coupons by Salmonella enterica and Listeria monocytogenes aftertreatment with 0.0001% Quillaja saponin alone. Buna N- StainlessStainless Day Bacteria rubber steel 304 steel 316 HDPE PC PVC Day 0 S.enterica 0.820 ± 0.091 ± 0.086 ± 0.090 ± 0.088 ± 0.071 ± 0.654 0.0320.005 0.009 0.003 0.006 L. monocytogenes 0.275 ± 0.074 ± 0.073 ± 0.074 ±0.076 ± 0.083 ± 0.136 0.019 0.006 0.005 0.010 0.028 Day 1 S. enterica0.514 ± 0.167 ± 0.157 ± 0.220 ± 0.243 ± 0.141 ± 0.249 0.039 0.057 0.1190.179 0.083 L. monocytogenes 0.315 ± 0.136 ± 0.146 ± 0.149 ± 0.177 ±0.092 ± 0.087 0.098 0.122 0.116 0.173 0.049 Day 3 S. enterica 0.581 ±0.505 ± 0.224 ± 0.314 ± 0.375 ± 0.358 ± 0.221 0.159 0.043 0.141 0.0500.100 L. monocytogenes 0.548 ± 0.295 ± 0.180 ± 0.553 ± 0.854 ± 0.391 ±0.236 0.012 0.041 0.381 0.572 0.217

TABLE 14 OD₆₀₀ values of crystal violet dye from biofilm formation onvarious coupons by Salmonella enterica and Listeria monocytogenes aftertreatment with 3% olive extract Buna N- Stainless Stainless Day Bacteriarubber steel 304 steel 316 HDPE PC PVC Day 0 S. enterica 0.532 ± 0.182 ±0.144 ± 0.219 ± 0.147 ± 0.119 ± 0.143 0.105 0.077 0.170 0.069 0.027 L.monocytogenes 0.253 ± 0.161 ± 0.127 ± 0.170 ± 0.124 ± 0.137 ± 0.0130.044 0.024 0.086 0.032 0.039 Day 1 S. enterica 0.444 ± 0.304 ± 0.434 ±0.404 ± 0.403 ± 0.219 ± 0.055 0.225 0.369 0.283 0.489 0.136 L.monocytogenes 0.488 ± 0.367 ± 0.524 ± 0.392 ± 0.150 ± 0.152 ± 0.0540.208 0.489 0.258 0.033 0.029 Day 3 S. enterica 0.678 ± 0.413 ± 0.231 ±0.322 ± 0.251 ± 0.354 ± 0.273 0.261 0.062 0.183 0.149 0.260 L.monocytogenes 0.506 ± 0.244 ± 0.246 ± 0.278 ± 0.393 ± 0.263 ± 0.1030.139 0.120 0.163 0.298 0.149

TABLE 15 OD₆₀₀ values of crystal violet dye from biofilm formation onvarious coupons by Salmonella enterica and Listeria monocytogenes aftertreatment with 0.3% oregano oil and 0.0001% saponin microemulsion BunaN- Stainless Stainless Day Bacteria rubber steel 304 steel 316 HDPE PCPVC Day 0 S. enterica 1.015 ± 0.556 ± 0.615 ± 0.949 ± 1.516 ± 0.934 ±0.379 0.092 0.239 0.737 0.191 0.428 L. monocytogenes 0.504 ± 0.239 ±0.676 ± 0.417 ± 0.775 ± 1.023 ± 0.019 0.018 0.651 0.103 0.470 0.444 Day1 S. enterica 0.637 ± 0.731 ± 0.562 ± 1.829 ± 2.011 ± 1.805 ± 0.3030.354 0.339 1.678 1.391 1.550 L. monocytogenes 0.640 ± 0.417 ± 0.414 ±1.640 ± 1.501 ± 0.793 ± 0.366 0.057 0.079 1.722 1.101 0.281 Day 3 S.enterica 0.612 ± 0.379 ± 0.294 ± 0.336 ± 0.307 ± 0.582 ± 0.275 0.0850.113 0.141 0.359 0.276 L. monocytogenes 0.476 ± 0.235 ± 0.233 ± 0.281 ±0.336 ± 0.712 ± 0.185 0.032 0.164 0.137 0.152 0.300

TABLE 16 OD₆₀₀ values of crystal violet dye recovered from couponsinoculated with Salmonella enterica after a two minute treatment with0.5%, 0.7% and 1.0% oregano oil and 0.0001% saponin microemulsions onDay 0, 1 and 3 Coupon Day 0 Day 1 Day 3 0.5% oregano oil microemulsion304 SS 0.085 0.056 0.134 316 SS 0.071 0.068 0.116 Buna N 0.484 0.4930.239 PVC 0.124 0.119 0.193 PC 0.339 0.201 0.105 HDPE 0.349 0.072 0.3290.7% oregano oil microemulsion 304 SS 0.158 0.248 0.780 316 SS 0.1030.198 0.681 Buna N 0.255 0.654 0.763 PVC 0.133 0.117 1.127 PC 0.3690.230 0.270 HDPE 0.115 0.074 0.609 1.0% oregano oil microemulsion 304 SS0.073 0.192 0.575 316 SS 0.077 0.083 0.611 Buna N 0.779 0.729 0.610 PVC0.553 0.101 0.881 PC 3.737 0.264 0.355 HDPE 0.362 0.072 0.290

The reduction in bacterial biofilm formation was also tested using adirect plating method. Biofilms were formed on six different foodcontact surface coupons (HDPE, Buna-N rubber, PC, PVC, and stainlesssteel 304 and 316) in separate 35 mm mini-petri dishes and evaluated atthree different time points (Day 0, 1, and 3). Biofilms were formedusing a 1:10 diluted TSB solution (10 mL) with either S. enterica or L.monocytogenes inoculum (100 μL). The coupons were also washed andtreated with antimicrobial solutions containing the plant-basedemulsifier and the essential oil/plant extracts at variousconcentrations. The diluted TSB was changed every 16-18 hours with new1:10 diluted TSB (10 mL). The coupons were rinsed in the antimicrobialsolution before adding them to the petri dishes containing the fresh,diluted TSB. After their specific time points, coupons were removedaseptically using sterile forceps from the petri dish. The coupons wererinsed by submerging in 25 mL of sterile deionized H₂O and swirled fivetimes to remove planktonic cells. After rinsing, they were placed into anew petri dish immersed in 10 mL of BPW. The coupons were sonicated for2 minutes on ice using different settings for each organism. Aftersonication, the sonicated solution was serially diluted using 0.1%peptone water and spread plated on TSA in duplicate. Plates wereincubated overnight at 37° C. for 24-48 hours, after which, the colonieswere counted, to establish the efficacy of the antimicrobial solutions(Tables 17-25). The results indicate that the plant-based antimicrobialmicroemulsions can prevent biofilm formation by S. enterica and L.monocytogenes on various produce contact surfaces.

TABLE 17 Enumeration of surviving population of Salmonella (Log CFU/mL)after biofilm formation upon exposure to 0.1% oregano oil + 0.0001%plant emulsifier microemulsion Coupons Day 0 Day 1 Stainless steel 3044.47 4.27 Stainless steel 316 4.25 4.26 PC 4.20 4.20 PVC 3.54 4.43 HDPE3.48 4.56 Buna rubber 3.59 4.79

TABLE 18 Enumeration of surviving population of Listeria monocytogenes(Log CFU/mL) after biofilm formation upon exposure to 0.1% oregano oil +0.0001% plant emulsifier microemulsion Coupons Day 0 Day 1 Stainlesssteel 304 4.28 4.27 Stainless steel 316 4.10 4.14 PC 3.83 4.40 PVC 3.704.65 Buna rubber 3.55 4.43 HDPE 3.85 4.72

TABLE 19 Enumeration of surviving population of Salmonella (Log CFU/mL)after biofilm formation upon exposure to 0.5% oregano oil or lemongrassoil + 0.0001% plant emulsifier microemulsion at Day 0 Coupons 0.5%oregano oil 0.5% lemongrass oil Stainless steel 304 <2Log 4.51 Stainlesssteel 316 <2Log 4.63 PC <2Log 4.64 PVC <2Log 4.63 Buna rubber <2Log 4.76HDPE <2Log 4.56

TABLE 20 Enumeration of surviving population of Listeria monocytogenes(Log CFU/mL) after biofilm formation upon exposure to 0.5% oregano oilor lemongrass oil + 0.0001% plant emulsifier microemulsion at Day 0Coupons 0.5% oregano oil 0.5% lemongrass oil Stainless steel 304 <2Log4.54 Stainless steel 316 <2Log 4.62 PC <2Log <2 Log PVC <2Log <2 LogBuna rubber <2Log 4.96 HDPE <2Log 4.65

TABLE 21 Population of survivors of Salmonella Newport (Log CFU/mL) onvarious food contact surfaces upon two-minute treatment with 0.5% plantantimicrobial with 0.0001% saponin microemulsions on Day 0, 1 and 3Cinna- Cinna- Oregano Lemon- malde- mon Coupons Carvacrol oil Citralgrass oil hyde Oil Day 0 304 SS 4.75 <1 4.32 4.53 4.31 3.38 316 SS 4.66<1 4.36 4.58 4.30 3.47 Buna N 4.19 <1 4.06 4.74 4.23 4.28 PVC 2.74 <13.49 4.96 3.93 4.37 PC <1 <1 3.25 4.57 4.06 4.37 HDPE <1 <1 3.44 4.874.27 4.38 Day 1 304 SS 4.26 4.39 4.52 4.48 4.45 4.36 316 SS 4.42 4.604.52 4.55 4.48 4.39 Buna N 4.65 4.81 4.34 4.83 4.87 4.76 PVC 4.24 4.134.27 <1 4.36 4.55 PC <1 <1 4.20 4.87 4.20 4.26 HDPE <1 <1 4.24 <1 4.244.34 Day 3 304 SS <1 <1 4.20 4.24 4.39 4.24 316 SS <1 <1 4.36 4.32 4.264.20 Buna N <1 <1 4.20 4.34 4.34 4.55 PVC <1 <1 4.27 <1 4.21 4.27 PC <1<1 3.52 4.62 3.75 3.26 HDPE <1 <1 3.56 <1 3.24 3.34

TABLE 22 Population of survivors of Salmonella Newport (Log CFU/mL) onvarious food contact surfaces upon two-minute treatment with 0.7% plantantimicrobial with 0.0001% saponin microemulsions on Day 0, 1 and 3Cinna- Cinna- Oregano Lemon- malde- mon Coupons Carvacrol oil Citralgrass oil hyde Oil Day 0 304 SS 4.57 4.40 4.23 3.71 4.0 4.30 316 SS 4.243.30 3.59 4.16 4.68 4.06 Buna N 4.44 4.33 4.52 4.05 4.08 3.77 PVC 4.634.01 3.24 3.71 <1 4.10 PC 4.18 3.77 3.59 4.07 4.11 4.11 HDPE 4.24 3.422.71 3.36 4.42 3.06 Day 1 304 SS <1 <1 3.36 3.66 3.68 3.32 316 SS <1 <13.24 3.15 3.0 3.20 Buna N <1 <1 3.52 3.20 3.24 3.38 PVC <1 <1 <1 <1 <1<1 PC <1 <1 <1 <1 3.29 <1 HDPE <1 <1 <1 <1 <1 <1 Day 3 304 SS <1 <1 <1<1 <1 <1 316 SS <1 <1 <1 <1 <1 <1 Buna N <1 <1 <1 <1 <1 <1 PVC <1 <1 <1<1 <1 <1 PC <1 <1 <1 <1 <1 <1 HDPE <1 <1 <1 <1 <1 <1

TABLE 23 Population of survivors of Salmonella Newport (Log CFU/mL) onvarious food contact surfaces upon two-minute treatment with 1% plantantimicrobial with 0.0001% saponin microemulsions on Day 0, 1 and 3Oregano Lemongrass Cinnamon Coupons Carvacrol oil Citral oilCinnamaldehyde Oil Day 0 304 SS <1 <1 3.91 3.36 <1 4.52 316 SS <1 <14.13 3.81 <1 4.38 Buna N <1 <1 3.26 4.30 <1 4.12 PVC <1 <1 3.89 3.42 <13.12 PC <1 <1 4.20 3.63 <1 3.60 HDPE <1 <1 4.45 3.39 <1 <1 Day 1 304 SS<1 <1 <1 <1 <1 <1 316 SS <1 <1 <1 <1 <1 <1 Buna N <1 <1 <1 <1 <1 <1 PVC<1 <1 <1 <1 <1 <1 PC <1 <1 <1 <1 <1 <1 HDPE <1 <1 <1 <1 <1 <1 Day 3 304SS <1 <1 <1 <1 <1 <1 316 SS <1 <1 <1 <1 <1 <1 Buna N <1 <1 <1 <1 <1 <1PVC <1 <1 <1 <1 <1 <1 PC <1 <1 <1 <1 <1 <1 HDPE <1 <1 <1 <1 <1 <1

TABLE 24 Population of survivors of Listeria monocytogenes (Log CFU/mL)on various food contact surfaces upon two-minute treatment with 5% plantextracts on Day 0, 1 and 3. Apple Grapeseed Olive Coupons extractextract extract Day 0 304 SS 4.24 4.38 3.68 316 SS 4.20 4.24 3.56 Buna N4.85 4.76 3.85 PVC 4.36 4.53 3.20 PC 4.38 4.26 3.24 HDPE 4.24 4.15 3.63Day 1 304 SS 3.64 3.26 <1 316 SS 3.66 3.15 <1 Buna N 3.85 3.20 <1 PVC3.25 3.24 <1 PC 3.16 4.36 <1 HDPE 3.35 4.53 <1 Day 3 304 SS <1 <1 <1 316SS <1 <1 <1 Buna N <1 <1 <1 PVC <1 <1 <1 PC <1 <1 <1 HDPE <1 <1 <1

TABLE 25 Population of survivors of Listeria monocytogenes (Log CFU/mL)on various food contact surfaces upon two-minute treatment with 7% plantextracts on Day 0, 1 and 3 Apple Grapeseed Olive Coupons extract extractextract Day 0 304 SS <1 <1 <1 316 SS <1 <1 <1 Buna N <1 <1 <1 PVC <1 <1<1 PC <1 <1 <1 HDPE <1 <1 <1 Day 1 304 SS <1 <1 <1 316 SS <1 <1 <1 BunaN <1 <1 <1 PVC <1 <1 <1 PC <1 <1 <1 HDPE <1 <1 <1 Day 3 304 SS <1 <1 <1316 SS <1 <1 <1 Buna N <1 <1 <1 PVC <1 <1 <1 PC <1 <1 <1 HDPE <1 <1 <1

Example 4 Efficacy of Plant-Based Antimicrobials at Low Concentrations

Pathogenic Salmonella enterica subspecies enterica serovar NewportLAJ160311, with the JJPX01.0014 PulseNet PFGE, isolated from oysters,was used for this study. S. Newport JJPX is resistant to ampicillin,chloramphenicol, streptomycin, sulfamethoxazole, tetracycline,amoxicillin-clavulanic acid, cephalothin, cefoxitin and ceftiofur, aswell as a decrease in susceptibility to ceftriaxone. S. Newport wasrevived using Tryptic Soy Broth (TSB), diluted using peptone water andplated on xylose lysine deoxycholate (XLD) agar. Essential oils used inthis study included lemongrass oil (LG), oregano oil (00) and cinnamonoil (CO) at 0.01-0.05% concentrations. Microemulsions of essential oilswere prepared by vigorously mixing them with 0.01% quillaja saponin insterile deionized water. Peracetic acid, sterile de-ionized water andsaponin were evaluated as controls.

The following concentrations of essential oils (individual andcombination treatments) were evaluated: 0.05%, 0.025% and 0.01% of eachof LG, CO, OO, LG+CO, LG+OO, CO+OO and LG+CO+OO (3×). Essential oilcombinations divided evenly to maintain a final concentration of 0.025%,denoted by the Greek symbol Σ, (ΣLG+CO, ΣLG+OO, ΣCO+OO and Σ3×) werealso evaluated in vitro. The individual and combination treatments atthese concentrations were compared against 10%, 50 ppm, 20 ppm, 10 ppm,and 5 ppm peracetic acid (PAA), 0.01% saponin and sterile deionizedwater (diH₂O).

Cryogenically frozen Salmonella Newport was revived and passed threetimes in TSB. Overnight cultures were also grown in TSB that wasincubated at 37° C. for 22 hours. After incubation, the overnightcultures were washed three times in PBS, by centrifuging at 4000 rpm for10 minutes. In a sterile stomacher bag, respective concentrations andcombinations of essential oils were added with 0.01% saponin diluted insterile diH₂O. PAA and 0.01% saponin controls were also diluted insterile diH₂O. The contents in stomacher bags were mixed thoroughly bypummeling in a stomacher at normal speed for 5 minutes to createmicroemulsions. After mixing, 9 mL of the individual and combinationessential oil microemulsions and controls were aliquoted in 15 mLcentrifuge tubes. An aliquot of 1 mL of washed overnight SalmonellaNewport culture was added to each tube. The treatments and controlsolutions were vortexed on high speed, diluted in 0.1% peptone water andspread plated on XLD agar for enumeration at time 0. Afterwards, thesolutions were incubated at 37° C. and samples taken for dilutions andspread plating at 3 hours and 24 hours. All XLD plates were incubated at37° C. overnight before enumeration.

Results are depicted in FIGS. 3-5. In earlier studies, plant essentialoils and their active components were used at concentrations of0.1-0.5%. Even though these antimicrobials were very effective againstfoodborne pathogenic bacteria at these concentrations, the objective ofthis investigation was to assess the effectiveness and any possiblesynergies of combinations of plant-based antimicrobials at lowerconcentrations in vitro against Salmonella enterica.

FIG. 3 shows the effectiveness of individual and combination essentialoil treatments at 0.05% concentration. No survivors of S. Newport weredetected with oregano oil (OO) treatment and all essential oil, dual,and triple, combination treatments immediately upon exposure (0 hourtime point) and continued thereafter. Both lemongrass (LG) and cinnamonoil (CO) treatments showed a reduction of >8-logs and >5-logs,respectively, at 0 hours. No survivors were detected at 3 hours for allthe treatments.

FIG. 4 shows the effectiveness of individual and combination treatmentsat 0.025% concentration. At this concentration, the combinationtreatments were more effective against S. Newport than individualtreatments. The triple (3×) combination showed a slightly betterreduction at 3 hours than any of the dual essential oil combinations. At24 hours, no survivors were detected in all the combination treatments(dual and triple).

FIG. 5 shows the efficacy of essential oil combinations giving a finalconcentration of 0.025%. The effectiveness of treatments in FIG. 5 wasreduced in comparison to those depicted in FIG. 4. Essential oils with afinal summating concentration of 0.025% showed a reduction of 1-log withΣLG+OO combination and less than a 2-log reduction with ΣLG+CO, ΣCO+OOand Σ3× combinations at 24 hours.

Example 5 Efficacy of Plant-Based Antimicrobials on Melon Rinds

Melon samples were harvested from farms located in Georgia, Arizona,Texas (2 locations—Weslaco and Uvalde), North Carolina, Indiana, andCalifornia. The tested melons included five cantaloupe varieties (F39,Infinite Gold SAKATA, Davinci SAKATA, Cruiser and PRIM), three honeydewvarieties (OC164, HD150 and Honeydew 252) and seven cantaloupe hybrids(TH1, TH2, TH3, TH4, TH5, TH6, and TH9).

Melon rinds were cut into pieces of 10 g and inoculated with 10⁶ CFU/mLof S. Newport or L. monocytogenes culture. The inoculated samples weredried for 1 hour to let the bacteria attach to the surface. The sampleswere then immersed in 5% olive extract or 0.5% oregano oil antimicrobialsolution and gently agitated for 2 minutes. Phosphate buffered saline(PBS) was used as a control. The samples were tested with three repeatsfor each experiment. After the treatment, the survivors of S. Newportand L. monocytogenes were enumerated at Days 0 and 3. The rind samplewas mixed with 90 mL of buffered peptone water (BPW) and stomached for 2minutes. Serial dilutions were made in 0.1% peptone water and aliquotsplated on xylose lysine deoxycholate (XLD) agar and Modified Oxford(MOX) formulation agar for enumeration of S. Newport and L.monocytogenes, respectively. The XLD and MOX plates were incubated at35° C. for 24-48 hours. The colonies were counted and calculated ascolonies forming units per gram (CFU/g).

The survival of S. Newport and L. monocytogenes are shown in Tables26-32 and 33-39, respectively. The plant-based antimicrobials reduced S.Newport and L. monocytogenes population on all the rind samples,regardless of the melon types, varieties, or growing locations. Comparedto the control wash (PBS), the plant-based antimicrobial treatmentscaused 2-3.6 and 1.6-3.7 log reductions in populations of Salmonella andL. monocytogenes, respectively. In most cases, the plant-basedantimicrobial treatments reduced the pathogen population to below thedetection limit (1 CFU/g) at day 3. In general, oregano oil had betterantimicrobial activity than olive extract. The antimicrobial treatmentswere more effective on Salmonella than on L. monocytogenes. Theantimicrobial treatments exhibited better reductions on honeydews thanon cantaloupes.

TABLE 26 Survival of Salmonella Newport (Log CFU/g) on Georgia grownmelon rinds after plant-based antimicrobial treatments Day 0 Day 3 0.5%0.5% Control 5% olive oregano Control 5% olive oregano Variety (PBS)extract oil (PBS) extract oil F39  4.48 ± 0.07* 2.30 ± 0.18 1.84 ± 0.334.59 ± 0.05  <1.00** 1.46 ± 0.56 OC164 4.00 ± 0.05 1.93 ± 0.16 1.06 ±0.10 3.98 ± 0.08 <1.00 <1.00 HD150 4.28 ± 0.12 1.94 ± 0.21 <1.00 4.08 ±0.10 <1.00 <1.00 Infinite Gold 4.36 ± 0.17 2.43 ± 0.14 1.86 ± 0.33 4.29± 0.12 2.02 ± 0.31 <1.00 SAKATA Honeydew 252 3.99 ± 0.13 1.13 ± 0.23<1.00 3.64 ± 0.23 <1.00 <1.00 Davinci 4.36 ± 0.10 2.59 ± 0.11 2.67 ±0.19 4.20 ± 0.09 2.15 ± 0.24 1.79 ± 0.38 SAKATA Cruiser 4.64 ± 0.03 1.23± 0.21 <1.00 4.60 ± 0.04 1.06 ± 0.10 1.13 ± 0.23 TH1 4.59 ± 0.05 1.65 ±0.14 1.65 ± 0.20 4.34 ± 0.20 <1.00 <1.00 TH2 4.09 ± 0.06 <1.00 1.90 ±0.10 4.02 ± 0.07 <1.00 <1.00 TH3 4.03 ± 0.02 1.06 ± 0.10 <1.00 4.10 ±0.13 <1.00 <1.00 TH4 4.55 ± 0.06 1.80 ± 0.12 1.16 ± 0.15 4.36 ± 0.071.06 ± 0.10 <1.00 TH5 4.00 ± 0.02 1.32 ± 0.15 <1.00 3.86 ± 0.08 <1.00<1.00 TH6 4.45 ± 0.13 1.06 ± 0.10 <1.00 4.32 ± 0.05 <1.00 <1.00 Data isshown as mean ± standard deviation. The detection limit for this studywas 1 Log CFU/g.

TABLE 27 Survival of Salmonella Newport (Log CFU/g) on Arizona grownmelon rinds after plant-based antimicrobial treatments Day 0 Day 3 0.5%0.5% Control 5% olive oregano Control 5% olive oregano Variety (PBS)extract oil (PBS) extract oil F39  4.42 ± 0.08* 2.33 ± 0.41 1.93 ± 0.284.46 ± 0.05 1.75 ± 0.27  <1.00** OC164 4.42 ± 0.07 2.74 ± 0.18 1.90 ±0.32 4.57 ± 0.06 1.71 ± 0.28 1.13 ± 0.23 HD150 4.40 ± 0.06 1.10 ± 0.171.13 ± 0.23 4.38 ± 0.12 <1.00 1.10 ± 0.17 Infinite Gold 4.39 ± 0.05 1.99± 0.41 2.21 ± 0.27 4.04 ± 0.01 <1.00 <1.00 SAKATA Honeydew 252 4.52 ±0.09 <1.00 <1.00 4.48 ± 0.08 <1.00 <1.00 Davinci 4.42 ± 0.03 2.62 ± 0.222.01 ± 0.41 4.36 ± 0.02 2.21 ± 0.28 <1.00 SAKATA Cruiser 4.30 ± 0.212.15 ± 0.43 1.33 ± 0.35 3.71 ± 0.17 <1.00 <1.00 TH1 4.03 ± 0.06 1.43 ±0.15 <1.00 3.96 ± 0.04 <1.00 <1.00 TH2 4.37 ± 0.03 2.01 ± 0.10 1.59 ±0.10 4.10 ± 0.05 <1.00 <1.00 TH4 4.32 ± 0.04 2.10 ± 0.13 1.70 ± 0.134.09 ± 0.01 1.24 ± 0.28 <1.00 TH6 4.19 ± 0.08 1.62 ± 0.15 1.19 ± 0.204.04 ± 0.04 1.06 ± 0.10 <1.00 Data is shown as mean ± standarddeviation. The detection limit for this study was 1 Log CFU/g.

TABLE 28 Survival of Salmonella Newport (Log CFU/g) on Weslaco, Texasgrown melon rinds after plant-based antimicrobial treatments Day 0 Day 30.5% 0.5% Control 5% olive oregano Control 5% olive oregano Variety(PBS) extract oil (PBS) extract oil F39  4.35 ± 0.06* 2.31 ± 0.22 1.55 ±0.33 4.47 ± 0.10 1.28 ± 0.27 1.16 ± 0.28 OC164 4.45 ± 0.07 1.80 ± 0.311.10 ± 0.17 4.40 ± 0.09 1.16 ± 0.28  <1.00** HD150 3.92 ± 0.09 1.48 ±0.26 1.06 ± 0.10 3.95 ± 0.16 <1.00 <1.00 Infinite Gold 4.50 ± 0.00 1.88± 0.22 1.58 ± 0.21 4.41 ± 0.08 1.41 ± 0.30 <1.00 SAKATA Honeydew 2524.08 ± 0.06 1.66 ± 0.17 1.06 ± 0.10 4.22 ± 0.08 1.10 ± 0.17 <1.00Davinci 4.49 ± 0.02 2.39 ± 0.17 1.51 ± 0.29 4.43 ± 0.06 1.35 ± 0.37<1.00 SAKATA Cruiser 4.47 ± 0.02 2.41 ± 0.21 2.15 ± 0.43 4.44 ± 0.082.56 ± 0.20 <1.00 PRIM 4.00 ± 0.02 <1.00 <1.00 3.88 ± 0.10 <1.00 <1.00Data is shown as mean ± standard deviation. The detection limit for thisstudy was 1 Log CFU/g.

TABLE 29 Survival of Salmonella Newport (Log CFU/g) on Uvalde, Texasgrown melon rinds after plant-based antimicrobial treatments Day 0 Day 30.5% 0.5% Control 5% olive oregano Control 5% olive oregano Variety(PBS) extract oil (PBS) extract oil F39  4.46 ± 0.05* 2.19 ± 0.28 1.13 ±0.23 4.47 ± 0.13 1.31 ± 0.39 1.10 ± 0.17 OC164 4.09 ± 0.04 1.19 ± 0.20 <1.00** 4.05 ± 0.06 <1.00 <1.00 HD150 4.29 ± 0.08 1.95 ± 0.15 <1.004.07 ± 0.08 1.19 ± 0.20 <1.00 Infinite Gold 4.52 ± 0.06 2.44 ± 0.17 2.40± 0.19 4.28 ± 0.11 2.05 ± 0.20 1.62 ± 0.22 SAKATA Honeydew 252 4.29 ±0.13 2.13 ± 0.28 1.42 ± 0.26 4.21 ± 0.08 1.94 ± 0.12 <1.00 Davinci 4.61± 0.02 2.60 ± 0.16 2.11 ± 0.27 4.60 ± 0.03 1.41 ± 0.37 <1.00 SAKATA TH64.01 ± 0.12 <1.00 <1.00 3.99 ± 0.04 <1.00 <1.00 TH9 3.97 ± 0.06 <1.001.19 ± 0.20 3.94 ± 0.08 <1.00 <1.00 Data is shown as mean ± standarddeviation. The detection limit for this study was 1 Log CFU/g.

TABLE 30 Survival of Salmonella Newport (Log CFU/g) on North Carolinagrown melon rinds after plant-based antimicrobial treatments Day 0 Day 30.5% 0.5% Control 5% olive oregano Control 5% olive oregano Variety(PBS) extract oil (PBS) extract oil F39  4.31 ± 0.11*  <1.00** <1.004.29 ± 0.11 <1.00 <1.00 OC164 4.44 ± 0.03 1.81 ± 0.27 1.16 ± 0.28 4.47 ±0.07 <1.00 <1.00 HD150 4.53 ± 0.09 <1.00 1.13 ± 0.23 4.57 ± 0.03 <1.00<1.00 Infinite Gold 4.42 ± 0.07 1.94 ± 0.30 1.78 ± 0.33 4.33 ± 0.17<1.00 <1.00 SAKATA Honeydew 252 4.07 ± 0.04 2.43 ± 0.32 <1.00 4.09 ±0.01 <1.00 <1.00 Davinci 4.63 ± 0.03 2.03 ± 0.16 1.37 ± 0.19 4.57 ± 0.02<1.00 <1.00 SAKATA TH2 4.19 ± 0.13 <1.00 <1.00 4.22 ± 0.07 <1.00 <1.00TH3 4.46 ± 0.05 1.66 ± 0.18 <1.00 4.16 ± 0.05 <1.00 <1.00 TH4 4.33 ±0.10 1.06 ± 0.10 <1.00 4.12 ± 0.09 <1.00 <1.00 TH5 4.46 ± 0.04 <1.001.53 ± 0.12 4.17 ± 0.14 <1.00 <1.00 TH6 4.45 ± 0.07 1.06 ± 0.10 <1.004.07 ± 0.09 <1.00 <1.00 Data is shown as mean ± standard deviation. Thedetection limit for this study was 1 Log CFU/g.

TABLE 31 Survival of Salmonella Newport (Log CFU/g) on Indiana grownmelon rinds after plant-based antimicrobial treatments Day 0 Day 3 0.5%0.5% Control 5% olive oregano Control 5% olive oregano Variety (PBS)extract oil (PBS) extract oil F39  4.16 ± 0.07* 1.19 ± 0.20  <1.00**4.02 ± 0.02 <1.00 <1.00 OC164 4.07 ± 0.08 <1.00 <1.00 4.00 ± 0.05 <1.00<1.00 HD150 4.46 ± 0.05 1.06 ± 0.10 <1.00 4.41 ± 0.10 <1.00 <1.00Infinite Gold 4.29 ± 0.09 1.41 ± 0.12 1.10 ± 0.17 4.07 ± 0.09 <1.00<1.00 SAKATA Honeydew 252 4.44 ± 0.02 <1.00 <1.00 4.29 ± 0.14 <1.00<1.00 Davinci 4.10 ± 0.06 1.86 ± 0.16 1.06 ± 0.10 3.98 ± 0.03 <1.00<1.00 SAKATA Data is shown as mean ± standard deviation. The detectionlimit for this study was 1 Log CFU/g.

TABLE 32 Survival of Salmonella Newport (Log CFU/g) on California grownmelon rinds after plant-based antimicrobial treatments Day 0 Day 3 0.5%0.5% Control 5% olive oregano Control 5% olive oregano Variety (PBS)extract oil (PBS) extract oil TH1  4.08 ± 0.11* 1.51 ± 0.22  <1.00**3.94 ± 0.02 <1.00 <1.00 TH2 3.99 ± 0.03 1.06 ± 0.10 <1.00 3.93 ± 0.03<1.00 <1.00 TH3 4.38 ± 0.05 1.12 ± 0.10 <1.00 4.06 ± 0.05 <1.00 <1.00TH4 4.31 ± 0.09 1.85 ± 0.11 1.85 ± 0.05 4.09 ± 0.10 1.06 ± 0.10 <1.00TH5 4.51 ± 0.05 1.19 ± 0.20 1.32 ± 0.15 4.51 ± 0.05 <1.00 <1.00 TH6 4.47± 0.04 <1.00 1.06 ± 0.10 4.31 ± 0.08 <1.00 <1.00 Data is shown as mean ±standard deviation. The detection limit for this study was 1 Log CFU/g.

TABLE 33 Survival of Listeria monocytogenes (Log CFU/g) on Georgia grownmelon rinds after plant-based antimicrobial treatments Day 0 Day 3 0.5%0.5% Control 5% olive oregano Control 5% olive oregano Variety (PBS)extract oil (PBS) extract oil F39  4.62 ± 0.06* 2.20 ± 0.08 2.58 ± 0.174.58 ± 0.02 2.42 ± 0.17 2.63 ± 0.17 OC164 4.30 ± 0.14 2.22 ± 0.27 2.43 ±0.18 4.54 ± 0.15 1.65 ± 0.24 2.67 ± 0.12 HD150 4.04 ± 0.03 2.64 ± 0.091.45 ± 0.44 4.04 ± 0.33 2.75 ± 0.07 1.53 ± 0.46 Infinite Gold 4.74 ±0.02 3.26 ± 0.04 3.42 ± 0.08 4.79 ± 0.09 3.09 ± 0.14 3.10 ± 0.18 SAKATAHoneydew 252 3.50 ± 0.25 2.24 ± 0.13 1.18 ± 0.31 2.65 ± 0.30 2.07 ± 0.23 <1.00** Davinci 4.47 ± 0.09 2.91 ± 0.03 2.95 ± 0.21 4.53 ± 0.03 2.89 ±0.12 2.79 ± 0.27 SAKATA Cruiser 4.69 ± 0.03 2.35 ± 0.19 2.44 ± 0.30 4.61± 0.10 2.57 ± 0.03 2.94 ± 0.10 TH1 4.54 ± 0.11 1.72 ± 0.23 2.41 ± 0.194.91 ± 0.06 <1.00 <1.00 TH2 4.57 ± 0.11 1.37 ± 0.41 2.69 ± 0.22 5.24 ±0.06 1.92 ± 0.09 2.08 ± 0.21 TH3 4.45 ± 0.08 2.22 ± 0.15 2.10 ± 0.325.03 ± 0.12 1.10 ± 0.17 1.59 ± 0.19 TH4 4.72 ± 0.07 2.42 ± 0.03 2.79 ±0.15 5.21 ± 0.13 <1.00 1.51 ± 0.20 TH5 4.60 ± 0.09 2.83 ± 0.13 2.98 ±0.10 4.79 ± 0.02 <1.00 <1.00 TH6 4.52 ± 0.11 2.58 ± 0.04 2.52 ± 0.154.61 ± 0.04 1.32 ± 0.15 1.43 ± 0.38 Data is shown as mean ± standarddeviation. The detection limit for this study was 1 Log CFU/g.

TABLE 34 Survival of Listeria monocytogenes (Log CFU/g) on Arizona grownmelon rinds after plant-based antimicrobial treatments Day 0 Day 3 0.5%0.5% Control 5% olive oregano Control 5% olive oregano Variety (PBS)extract oil (PBS) extract oil F39  4.86 ± 0.02* 3.38 ± 0.31 3.23 ± 0.164.91 ± 0.03 2.55 ± 0.07 1.57 ± 0.26 OC164 4.83 ± 0.07 2.65 ± 0.32 2.79 ±0.20 4.94 ± 0.06 1.81 ± 0.23 1.84 ± 0.18 HD150 4.85 ± 0.12 1.06 ± 0.102.15 ± 0.25 4.96 ± 0.19 1.18 ± 0.31 1.44 ± 0.28 Infinite Gold 4.69 ±0.05 3.25 ± 0.21 3.24 ± 0.14 4.80 ± 0.05 3.00 ± 0.06 2.32 ± 0.39 SAKATAHoneydew 252 4.69 ± 0.05 1.22 ± 0.38 <1.00** 4.70 ± 0.10 <1.00 <1.00Davinci 4.49 ± 0.07 2.78 ± 0.12 2.58 ± 0.16 4.44 ± 0.10 2.51 ± 0.23 2.44± 0.21 SAKATA TH1 4.48 ± 0.06 2.13 ± 0.23 2.57 ± 0.17 4.84 ± 0.09 1.32 ±0.15 1.69 ± 0.11 TH2 4.61 ± 0.09 2.70 ± 0.10 2.46 ± 0.09 4.93 ± 0.081.67 ± 0.12 <1.00 TH4 4.73 ± 0.07 2.72 ± 0.09 2.85 ± 0.11 5.04 ± 0.041.98 ± 0.25 <1.00 TH6 4.42 ± 0.08 2.46 ± 0.10 2.60 ± 0.17 4.89 ± 0.02<1.00 1.24 ± 0.28 Data is shown as mean ± standard deviation. Thedetection limit for this study was 1 Log CFU/g.

TABLE 35 Survival of Listeria monocytogenes (Log CFU/g) on Weslaco,Texas grown melon rinds after plant-based antimicrobial treatments Day 0Day 3 0.5% 0.5% Control 5% olive oregano Control 5% olive oreganoVariety (PBS) extract oil (PBS) extract oil F39  4.28 ± 0.27* 2.84 ±0.14 2.65 ± 0.18 4.40 ± 0.08 2.34 ± 0.20 2.18 ± 0.27 OC164 4.37 ± 0.331.54 ± 0.18 2.46 ± 0.22 4.58 ± 0.08 2.59 ± 0.25 1.10 ± 0.17 HD150 4.28 ±0.07 2.63 ± 0.23 2.39 ± 0.35 4.58 ± 0.09 1.82 ± 0.19 <1.00** InfiniteGold 4.21 ± 0.10 2.14 ± 0.11 2.13 ± 0.26 4.25 ± 0.11 1.90 ± 0.27 2.03 ±0.13 SAKATA Honeydew 252 4.32 ± 0.12 2.83 ± 0.16 1.20 ± 0.35 4.10 ± 0.222.08 ± 0.28 1.16 ± 0.28 Davinci 4.73 ± 0.05 3.13 ± 0.20 3.18 ± 0.36 4.87± 0.12 2.01 ± 0.22 2.23 ± 0.40 SAKATA Cruiser 4.66 ± 0.04 2.71 ± 0.233.06 ± 0.21 4.60 ± 0.11 2.16 ± 0.28 1.74 ± 0.18 PRIM 4.73 ± 0.13 2.02 ±0.19 2.23 ± 0.29 4.86 ± 0.13 1.42 ± 0.21 2.12 ± 0.24 Data is shown asmean ± standard deviation. The detection limit for this study was 1 LogCFU/g.

TABLE 36 Survival of Listeria monocytogenes (Log CFU/g) on Uvalde, Texasgrown melon rinds after plant-based antimicrobial treatments Day 0 Day 30.5% 0.5% Control 5% olive oregano Control 5% olive oregano Variety(PBS) extract oil (PBS) extract oil F39  4.61 ± 0.07* 2.86 ± 0.11 3.07 ±0.24 4.40 ± 0.26 2.88 ± 0.19 2.66 ± 0.28 OC164 3.99 ± 0.02 1.13 ± 0.231.99 ± 0.28 4.06 ± 0.05  <1.00** 1.06 ± 0.10 HD150 3.97 ± 0.02 1.61 ±0.24 2.13 ± 0.22 4.04 ± 0.11 1.31 ± 0.28 1.20 ± 0.35 Infinite Gold 4.48± 0.11 2.55 ± 0.16 2.71 ± 0.19 4.55 ± 0.06 2.67 ± 0.15 1.80 ± 0.24SAKATA Honeydew 252 4.31 ± 0.28 1.28 ± 0.34 1.10 ± 0.17 4.52 ± 0.14<1.00 <1.00 Davinci 4.62 ± 0.06 3.03 ± 0.13 3.48 ± 0.03 4.60 ± 0.02 3.15± 0.08 2.74 ± 0.22 SAKATA TH6 4.14 ± 0.14 <1.00 1.06 ± 0.10 4.38 ± 0.13<1.00 1.06 ± 0.10 TH9 3.86 ± 0.11 1.58 ± 0.17 2.17 ± 0.23 4.18 ± 0.091.06 ± 0.10 <1.00 Data is shown as mean ± standard deviation. Thedetection limit for this study was 1 Log CFU/g.

TABLE 37 Survival of Listeria monocytogenes (Log CFU/g) on NorthCarolina grown melon rinds after plant-based antimicrobial treatmentsDay 0 Day 3 0.5% 0.5% Control 5% olive oregano Control 5% olive oreganoVariety (PBS) extract oil (PBS) extract oil F39  4.73 ± 0.03* 1.63 ±0.22 2.18 ± 0.18 4.78 ± 0.10  <1.00** <1.00 OC164 4.42 ± 0.29 2.31 ±0.26 1.38 ± 0.37 4.25 ± 0.23 <1.00 <1.00 HD150 4.19 ± 0.19 1.45 ± 0.371.18 ± 0.31 4.19 ± 0.23 <1.00 1.06 ± 0.10 Infinite Gold 4.46 ± 0.05 2.28± 0.26 2.34 ± 0.16 4.05 ± 0.11 <1.00 1.10 ± 0.17 SAKATA Honeydew 2524.04 ± 0.08 1.20 ± 0.35 1.13 ± 0.23 4.30 ± 0.22 <1.00 <1.00 Davinci 4.72± 0.05 3.13 ± 0.10 3.12 ± 0.21 4.82 ± 0.14 2.85 ± 0.24 2.90 ± 0.43SAKATA TH2 4.55 ± 0.05 1.44 ± 0.24 2.23 ± 0.20 4.75 ± 0.09 <1.00 <1.00TH3 4.43 ± 0.04 1.94 ± 0.25 2.07 ± 0.18 4.69 ± 0.08 <1.00 <1.00 TH4 4.25± 0.19 1.06 ± 0.10 1.98 ± 0.14 4.78 ± 0.14 1.06 ± 0.10 <1.00 TH5 4.42 ±0.12 1.88 ± 0.19 2.34 ± 0.16 4.53 ± 0.09 1.06 ± 0.10 1.41 ± 0.12 TH64.41 ± 0.02 1.35 ± 0.16 1.23 ± 0.21 4.52 ± 0.11 <1.00 1.06 ± 0.10 Datais shown as mean ± standard deviation. The detection limit for thisstudy was 1 Log CFU/g.

TABLE 38 Survival of Listeria monocytogenes (Log CFU/g) on Indiana grownmelon rinds after plant-based antimicrobial treatments Day 0 Day 3 0.5%0.5% Control 5% olive oregano Control 5% olive oregano Variety (PBS)extract oil (PBS) extract oil F39  4.72 ± 0.07* 2.25 ± 0.08 2.18 ± 0.144.98 ± 0.05 1.90 ± 0.10  <1.00** OC164 4.52 ± 0.17 1.89 ± 0.77 1.06 ±0.10 4.84 ± 0.12 <1.00 <1.00 HD150 4.06 ± 0.06 1.58 ± 0.17 1.16 ± 0.154.83 ± 0.07 <1.00 <1.00 Infinite Gold 4.88 ± 0.08 2.68 ± 0.08 2.51 ±0.07 4.85 ± 0.08 2.11 ± 0.12 <1.00 SAKATA Honeydew 252 4.44 ± 0.07 1.16± 0.15 <1.00 4.70 ± 0.13 <1.00 <1.00 Davinci 4.76 ± 0.06 2.86 ± 0.071.94 ± 0.15 4.93 ± 0.06 1.78 ± 0.11 <1.00 SAKATA Data is shown as mean ±standard deviation. The detection limit for this study was 1 Log CFU/g.

TABLE 39 Survival of Listeria monocytogenes (Log CFU/g) on Californiagrown melon rinds after plant-based antimicrobial treatments Day 0 Day 30.5% 0.5% Control 5% olive oregano Control 5% olive oregano Variety(PBS) extract oil (PBS) extract oil TH1  4.14 ± 0.08* 1.90 ± 0.16 1.82 ±0.13 4.27 ± 0.06 1.54 ± 0.18  <1.00** TH2 4.52 ± 0.09 1.96 ± 0.17 2.24 ±0.20 4.42 ± 0.08 1.57 ± 0.15 <1.00 TH3 4.75 ± 0.10 2.21 ± 0.19 2.09 ±0.16 4.99 ± 0.07 <1.00 <1.00 TH4 4.42 ± 0.03 1.86 ± 0.20 2.31 ± 0.164.62 ± 0.11 <1.00 <1.00 TH5 4.59 ± 0.04 2.55 ± 0.07 2.44 ± 0.04 4.76 ±0.02 2.03 ± 0.19 <1.00 TH6 4.60 ± 0.07 1.48 ± 0.18 1.35 ± 0.16 4.55 ±0.07 1.06 ± 0.10 <1.00 Data is shown as mean ± standard deviation. Thedetection limit for this study was 1 Log CFU/g.

In view of the many possible embodiments to which the principles of thedisclosure may be applied, it should be recognized that the illustratedembodiments are only examples and should not be taken as limiting thescope of the invention. Rather, the scope of the invention is defined bythe following claims. We therefore claim as our invention all that comeswithin the scope and spirit of these claims.

We claim:
 1. An antimicrobial composition comprising: one or moreplant-derived compounds; and an emulsifier.
 2. The antimicrobialcomposition of claim 1, further comprising ozone, one or more plantessential oils, or a combination thereof.
 3. The antimicrobialcomposition of claim 1, wherein the one or more plant-derived compoundsis present in the composition at a concentration of about 0.01-1% (v/v).4. The antimicrobial composition of claim 1, wherein: the one or moreplant-derived compounds is carvacrol, eugenol, citral, cinnamaldehyde,or a combination of two or more thereof.
 5. The antimicrobialcomposition of claim 1, wherein the emulsifier is present in thecomposition at a concentration of about 0.0001-1% (v/v).
 6. Theantimicrobial composition of claim 1, wherein the emulsifier is saponin.7. The composition of claim 1, wherein the composition is present in afood item.
 8. A method of killing a microorganism, comprising contactingthe microorganism with the antimicrobial composition of claim
 1. 9. Anantimicrobial composition comprising one or more plant extracts.
 10. Theantimicrobial composition of claim 9, further comprising ozone, anemulsifier, one or more plant essential oils, or a combination of two ormore thereof.
 11. The antimicrobial composition of claim 9, wherein theone or more plant extracts is present in the composition at aconcentration of about 1-10% (v/v).
 12. The antimicrobial composition ofclaim 9, wherein the one or more plant extracts is olive extract, appleextract, grapeseed extract, potato peel extract, melon peel extract,apple peel extract, orange peel extract, hibiscus aqueous extract, greentea, black tea, or decaffeinated black tea extract, mushroom extract,rice hull smoke extract, or a combination of two or more thereof. 13.The composition of claim 9, wherein the composition is present in a fooditem.
 14. A method of killing a microorganism, comprising contacting themicroorganism with the antimicrobial composition of claim
 9. 15. Themethod of claim 14, wherein the antimicrobial composition is insolution, a powder, a vapor phase, a fog state, or an edible film. 16.The method of claim 9, wherein the microorganism is a bacterium,bacterial spore, helminth, protozoan, fungus, fungal spore, or virus.17. The method of claim 9, wherein the bacterium is Salmonella enterica,Escherichia coli, Listeria monocytogenes, Staphylococcus aureus,Clostridium perfringens, Clostridium botulinum, Bacillus cereus, Vibrioparahaemolyticus, Vibrio cholerae, Vibrio vulnificus, Campylobacter,Shigella, or Shiga toxin-producing E. coli.
 18. The method of claim 9,wherein the microorganism is present in the form of a biofilm.
 19. Themethod of claim 9, wherein the microorganism is present on a food item,a food contact surface, or a non-food contact surface.
 20. The method ofclaim 9, wherein the antimicrobial composition is used 1 to 5 times.